Virtually Healthcare HL7 FHIR Implementation Guide
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Virtually Healthcare HL7 FHIR Implementation Guide, published by Virtually Healthcare. This guide is not an authorized publication; it is the continuous build for version 0.1.0-current built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/Virtually-Healthcare/Virtually-Healthcare-FHIR-Implementation-Guide/ and changes regularly. See the Directory of published versions

Resource Profile: Observation - Detailed Descriptions

Draft as of 2024-11-06

Definitions for the Observation resource profile.

Guidance on how to interpret the contents of this table can be found here

0. Observation
2. Observation.identifier
NoteThis is a business identifier, not a resource identifier (see discussion)
Control1..?
Must Supporttrue
SlicingThis element introduces a set of slices on Observation.identifier. The slices areUnordered and Closed, and can be differentiated using the following discriminators:
  • pattern @ system
  • 4. Observation.identifier:CommonResourceIdentifiers
    Slice NameCommonResourceIdentifiers
    ShortCommon Resource Identifiers
    NoteThis is a business identifier, not a resource identifier (see discussion)
    Control0..*
    TypeIdentifier(Common Resource Identifiers)
    6. Observation.code
    Obligations
      ObligationsActor
      SHALL:populate-if-knownClinical Data Repository
      SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
      Standard StatusNormative (from Normative)
      8. Observation.subject
      10. Observation.subject.reference
      Control1..?
      Must Supporttrue
      12. Observation.subject.identifier
      NoteThis is a business identifier, not a resource identifier (see discussion)
      TypeIdentifier(NHS, HCSN and CHI Numbers)
      14. Observation.effective[x]
      Control1..?
      TypedateTime, Period, Timing, instant
      [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
      Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
      Obligations
        ObligationsActor
        SHALL:populate-if-knownClinical Data Repository
        SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
        Standard StatusNormative (from Normative)
        16. Observation.performer
        Control1..?
        TypeReference(Practitioner, Patient)
        18. Observation.performer.identifier
        NoteThis is a business identifier, not a resource identifier (see discussion)
        TypeIdentifier(UK Professional License, NHS, HCSN and CHI Numbers, Staff Enterprise Number)
        20. Observation.value[x]
        [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
        Obligations
          ObligationsActor
          SHALL:populate-if-knownClinical Data Repository
          SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
          Standard StatusNormative (from Normative)

          Guidance on how to interpret the contents of this table can be found here

          0. Observation
          Definition

          Measurements and simple assertions made about a patient, device or other subject.

          ShortMeasurements and simple assertions
          Comments

          Used for simple observations such as device measurements, laboratory atomic results, vital signs, height, weight, smoking status, comments, etc. Other resources are used to provide context for observations such as laboratory reports, etc.

          Control0..*
          Is Modifierfalse
          Alternate NamesVital Signs, Measurement, Results, Tests
          Invariantsdom-2: If the resource is contained in another resource, it SHALL NOT contain nested Resources (contained.contained.empty())
          dom-4: If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated (contained.meta.versionId.empty() and contained.meta.lastUpdated.empty())
          dom-3: If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource (contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().as(canonical) | %resource.descendants().as(uri) | %resource.descendants().as(url))) or descendants().where(reference = '#').exists() or descendants().where(as(canonical) = '#').exists() or descendants().where(as(canonical) = '#').exists()).not()).trace('unmatched', id).empty())
          dom-6: A resource should have narrative for robust management (text.`div`.exists())
          dom-5: If a resource is contained in another resource, it SHALL NOT have a security label (contained.meta.security.empty())
          obs-7: If Observation.code is the same as an Observation.component.code then the value element associated with the code SHALL NOT be present (value.empty() or component.code.where(coding.intersect(%resource.code.coding).exists()).empty())
          obs-6: dataAbsentReason SHALL only be present if Observation.value[x] is not present (dataAbsentReason.empty() or value.empty())
          obs-6: dataAbsentReason SHALL only be present if Observation.value[x] is not present (dataAbsentReason.empty() or value.empty())
          obs-7: If Observation.code is the same as an Observation.component.code then the value element associated with the code SHALL NOT be present (value.empty() or component.code.where(coding.intersect(%resource.code.coding).exists()).empty())
          2. Observation.implicitRules
          Definition

          A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content. Often, this is a reference to an implementation guide that defines the special rules along with other profiles etc.

          ShortA set of rules under which this content was created
          Comments

          Asserting this rule set restricts the content to be only understood by a limited set of trading partners. This inherently limits the usefulness of the data in the long term. However, the existing health eco-system is highly fractured, and not yet ready to define, collect, and exchange data in a generally computable sense. Wherever possible, implementers and/or specification writers should avoid using this element. Often, when used, the URL is a reference to an implementation guide that defines these special rules as part of it's narrative along with other profiles, value sets, etc.

          Control0..1
          This element is affected by the following invariants: ele-1
          Typeuri
          Is Modifiertrue because This element is labeled as a modifier because the implicit rules may provide additional knowledge about the resource that modifies it's meaning or interpretation
          Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
          Summarytrue
          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
          4. Observation.extension:triggeredByR5
          Slice NametriggeredByR5
          Definition

          Identifies the observation(s) that triggered the performance of this observation.

          ShortTriggering observation(s). This is a R5 backport.
          Comments

          There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

          Control0..*
          This element is affected by the following invariants: ele-1
          TypeExtension(Extension UK Core Observation Triggered By) (Complex Extension)
          Standard StatusNormative (from Normative)
          Alternate Namesextensions, user content
          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
          ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
          6. Observation.extension:triggeredByR5.extension
          Definition

          May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

          ShortAdditional content defined by implementations
          Comments

          There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

          Control20..*
          This element is affected by the following invariants: ele-1
          TypeExtension
          Is Modifierfalse
          Standard StatusNormative (from Normative)
          Alternate Namesextensions, user content
          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
          ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
          ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
          SlicingThis element introduces a set of slices on Observation.extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
          • value @ url
          • 8. Observation.extension:triggeredByR5.extension:observation
            Slice Nameobservation
            Definition

            Reference to the triggering observation.

            ShortTriggering observationAdditional content defined by implementations
            Comments

            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

            Control10..1*
            This element is affected by the following invariants: ele-1
            TypeExtension
            Is Modifierfalse
            Standard StatusNormative (from Normative)
            Alternate Namesextensions, user content
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            10. Observation.extension:triggeredByR5.extension:observation.url
            Definition

            Source of the definition for the extension code - a logical name or a URL.

            Shortidentifies the meaning of the extension
            Comments

            The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

            Control1..1
            Typeuri
            Is Modifierfalse
            XML FormatIn the XML format, this property is represented as an attribute.
            Fixed Valueobservation
            12. Observation.extension:triggeredByR5.extension:observation.value[x]
            Definition

            A reference to the triggering observation.


            Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

            ShortTriggering observation.Value of extension
            Control10..1
            This element is affected by the following invariants: ele-1
            TypeReference(Observation), date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, Coding, SampledData, id, positiveInt, Distance, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, CodeableConcept, ParameterDefinition, dateTime, code, string, Contributor, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, Signature, unsignedInt, time
            [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
            Is Modifierfalse
            Standard StatusNormative (from Normative)
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            14. Observation.extension:triggeredByR5.extension:type
            Slice Nametype
            Definition

            The type of trigger. Reflex | Repeat | Re-run.

            Shortreflex | repeat | re-runAdditional content defined by implementations
            Comments

            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

            Control10..1*
            This element is affected by the following invariants: ele-1
            BindingThe codes SHALL be taken from For codes, see observation-triggeredbytype
            (required to http://hl7.org/fhir/ValueSet/observation-triggeredbytype)
            TypeExtension
            Is Modifierfalse
            Standard StatusNormative (from Normative)
            Alternate Namesextensions, user content
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            16. Observation.extension:triggeredByR5.extension:type.url
            Definition

            Source of the definition for the extension code - a logical name or a URL.

            Shortidentifies the meaning of the extension
            Comments

            The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

            Control1..1
            Typeuri
            Is Modifierfalse
            XML FormatIn the XML format, this property is represented as an attribute.
            Fixed Valuetype
            18. Observation.extension:triggeredByR5.extension:type.value[x]
            Definition

            The type of trigger. Reflex | Repeat | Re-run


            Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

            ShortThe type of trigger. Reflex | Repeat | Re-runValue of extension
            Control10..1
            This element is affected by the following invariants: ele-1
            Typecode, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, Coding, SampledData, id, positiveInt, Distance, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, CodeableConcept, ParameterDefinition, dateTime, string, Contributor, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, Signature, unsignedInt, time
            [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
            Is Modifierfalse
            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
            Standard StatusNormative (from Normative)
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            20. Observation.extension:triggeredByR5.extension:reason
            Slice Namereason
            Definition

            Provides the reason why this observation was performed as a result of the observation(s) referenced.

            ShortReason that the observation was triggeredAdditional content defined by implementations
            Comments

            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

            Control0..1*
            This element is affected by the following invariants: ele-1
            TypeExtension
            Is Modifierfalse
            Standard StatusNormative (from Normative)
            Alternate Namesextensions, user content
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            22. Observation.extension:triggeredByR5.extension:reason.url
            Definition

            Source of the definition for the extension code - a logical name or a URL.

            Shortidentifies the meaning of the extension
            Comments

            The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

            Control1..1
            Typeuri
            Is Modifierfalse
            XML FormatIn the XML format, this property is represented as an attribute.
            Fixed Valuereason
            24. Observation.extension:triggeredByR5.extension:reason.value[x]
            Definition

            Provides the reason why this observation was performed as a result of the observation referenced.


            Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

            ShortReason that the observation was triggered.Value of extension
            Control10..1
            This element is affected by the following invariants: ele-1
            Typestring, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, Coding, SampledData, id, positiveInt, Distance, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, CodeableConcept, ParameterDefinition, dateTime, code, Contributor, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, Signature, unsignedInt, time
            [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
            Is Modifierfalse
            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
            Standard StatusNormative (from Normative)
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            26. Observation.extension:triggeredByR5.url
            Definition

            Source of the definition for the extension code - a logical name or a URL.

            Shortidentifies the meaning of the extension
            Comments

            The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

            Control1..1
            Typeuri
            Is Modifierfalse
            XML FormatIn the XML format, this property is represented as an attribute.
            Fixed Valuehttp://hl7.org/fhir/5.0/StructureDefinition/extension-Observation.triggeredBy
            28. Observation.extension:triggeredByR5.value[x]
            Definition

            Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

            ShortValue of extension
            Control0..01
            This element is affected by the following invariants: ele-1
            TypeChoice of: base64Binary, boolean, canonical, code, date, dateTime, decimal, id, instant, integer, markdown, oid, positiveInt, string, time, unsignedInt, uri, url, uuid, Address, Age, Annotation, Attachment, CodeableConcept, Coding, ContactPoint, Count, Distance, Duration, HumanName, Identifier, Money, Period, Quantity, Range, Ratio, Reference, SampledData, Signature, Timing, ContactDetail, Contributor, DataRequirement, Expression, ParameterDefinition, RelatedArtifact, TriggerDefinition, UsageContext, Dosage, Meta
            Is Modifierfalse
            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
            Standard StatusNormative (from Normative)
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            30. Observation.extension:bodyStructureR5
            Slice NamebodyStructureR5
            Definition

            Indicates the body structure on the subject's body where the observation was made (i.e. the target site).

            ShortObserved body structure. This is a R5 backport.
            Comments

            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

            Control0..1
            This element is affected by the following invariants: ele-1
            TypeExtension(Extension UK Core Observation Body Structure) (Extension Type: Reference(BodyStructure))
            Standard StatusNormative (from Normative)
            Alternate Namesextensions, user content
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            32. Observation.modifierExtension
            Definition

            May be used to represent additional information that is not part of the basic definition of the resource and that modifies the understanding of the element that contains it and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

            Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

            ShortExtensions that cannot be ignored
            Comments

            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

            Control0..*
            This element is affected by the following invariants: ele-1
            TypeExtension
            Is Modifiertrue because Modifier extensions are expected to modify the meaning or interpretation of the resource that contains them
            Standard StatusNormative (from Normative)
            Requirements

            Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

            Alternate Namesextensions, user content
            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
            SlicingThis element introduces a set of slices on Observation.modifierExtension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
            • value @ url
            • 34. Observation.identifier
              Definition

              A unique identifier assigned to this observation.

              ShortBusiness Identifier for observation
              NoteThis is a business identifier, not a resource identifier (see discussion)
              Control10..*
              This element is affected by the following invariants: ele-1
              TypeIdentifier
              Is Modifierfalse
              Must Supporttrue
              Summarytrue
              Requirements

              Allows observations to be distinguished and referenced.

              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
              SlicingThis element introduces a set of slices on Observation.identifier. The slices areUnordered and Closed, and can be differentiated using the following discriminators:
              • pattern @ system
              • 36. Observation.identifier:CommonResourceIdentifiers
                Slice NameCommonResourceIdentifiers
                Definition

                An identifier - identifies some entity uniquely and unambiguously. Typically this is used for business identifiers.


                A unique identifier assigned to this observation.

                ShortCommon Resource IdentifiersBusiness Identifier for observation
                NoteThis is a business identifier, not a resource identifier (see discussion)
                Control0..*
                This element is affected by the following invariants: ele-1
                TypeIdentifier(Common Resource Identifiers)
                Is Modifierfalse
                Requirements

                Allows observations to be distinguished and referenced.

                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                38. Observation.status
                Definition

                The status of the result value.

                Shortregistered | preliminary | final | amended +
                Comments

                This element is labeled as a modifier because the status contains codes that mark the resource as not currently valid.

                Control1..1
                This element is affected by the following invariants: ele-1
                BindingThe codes SHALL be taken from ObservationStatushttp://hl7.org/fhir/ValueSet/observation-status|4.0.1
                (required to http://hl7.org/fhir/ValueSet/observation-status|4.0.1)

                Codes providing the status of an observation.

                Typecode
                Is Modifiertrue because This element is labeled as a modifier because it is a status element that contains status entered-in-error which means that the resource should not be treated as valid
                Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                Must Supporttrue
                Summarytrue
                Requirements

                Need to track the status of individual results. Some results are finalized before the whole report is finalized.

                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                40. Observation.category
                Definition

                A code that classifies the general type of observation being made.

                ShortClassification of type of observation
                Comments

                In addition to the required category valueset, this element allows various categorization schemes based on the owner’s definition of the category and effectively multiple categories can be used at once. The level of granularity is defined by the category concepts in the value set.

                Control0..*
                This element is affected by the following invariants: ele-1
                BindingThe codes SHOULD be taken from ObservationCategoryCodeshttp://hl7.org/fhir/ValueSet/observation-category
                (preferred to http://hl7.org/fhir/ValueSet/observation-category)

                Codes for high level observation categories.

                TypeCodeableConcept
                Is Modifierfalse
                Must Supporttrue
                Requirements

                Used for filtering what observations are retrieved and displayed.

                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                42. Observation.code
                Definition

                Describes what was observed. Sometimes this is called the observation "name".

                ShortType of observation (code / type)
                Comments

                All code-value and, if present, component.code-component.value pairs need to be taken into account to correctly understand the meaning of the observation.

                Control1..1
                This element is affected by the following invariants: ele-1
                BindingThe codes SHOULD be taken from For example codes, see UK Core Observation Typehttp://hl7.org/fhir/ValueSet/observation-codes
                (preferred to https://fhir.hl7.org.uk/ValueSet/UKCore-ObservationType)

                A code from the SNOMED Clinical Terminology UK coding system describing a type of observation


                Codes identifying names of simple observations.

                TypeCodeableConcept
                Is Modifierfalse
                Must Supporttrue
                Obligations
                  ObligationsActor
                  SHALL:populate-if-knownClinical Data Repository
                  SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
                  Summarytrue
                  Requirements

                  Knowing what kind of observation is being made is essential to understanding the observation.

                  Alternate NamesName
                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                  44. Observation.subject
                  Definition

                  The patient, or group of patients, location, or device this observation is about and into whose record the observation is placed. If the actual focus of the observation is different from the subject (or a sample of, part, or region of the subject), the focus element or the code itself specifies the actual focus of the observation.

                  ShortWho and/or what the observation is about
                  Comments

                  One would expect this element to be a cardinality of 1..1. The only circumstance in which the subject can be missing is when the observation is made by a device that does not know the patient. In this case, the observation SHALL be matched to a patient through some context/channel matching technique, and at this point, the observation should be updated.

                  Control0..1
                  This element is affected by the following invariants: ele-1
                  TypeReference(Patient, Group, Device, Location)
                  Is Modifierfalse
                  Must Supporttrue
                  Must Support TypesNo must-support rules about the choice of types/profiles
                  Summarytrue
                  Requirements

                  Observations have no value if you don't know who or what they're about.

                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                  ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                  46. Observation.subject.reference
                  Definition

                  A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

                  ShortLiteral reference, Relative, internal or absolute URL
                  Comments

                  Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "/[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

                  Control10..1
                  This element is affected by the following invariants: ref-1
                  Typestring
                  Is Modifierfalse
                  Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                  Must Supporttrue
                  Summarytrue
                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                  48. Observation.subject.identifier
                  Definition

                  An identifier - identifies some entity uniquely and unambiguously. Typically this is used for business identifiers.


                  An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.

                  ShortAn identifier intended for computationLogical reference, when literal reference is not known
                  Comments

                  When an identifier is provided in place of a reference, any system processing the reference will only be able to resolve the identifier to a reference if it understands the business context in which the identifier is used. Sometimes this is global (e.g. a national identifier) but often it is not. For this reason, none of the useful mechanisms described for working with references (e.g. chaining, includes) are possible, nor should servers be expected to be able resolve the reference. Servers may accept an identifier based reference untouched, resolve it, and/or reject it - see CapabilityStatement.rest.resource.referencePolicy.

                  When both an identifier and a literal reference are provided, the literal reference is preferred. Applications processing the resource are allowed - but not required - to check that the identifier matches the literal reference

                  Applications converting a logical reference to a literal reference may choose to leave the logical reference present, or remove it.

                  Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

                  NoteThis is a business identifier, not a resource identifier (see discussion)
                  Control0..1
                  This element is affected by the following invariants: ele-1
                  TypeIdentifier(NHS, HCSN and CHI Numbers)
                  Is Modifierfalse
                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                  50. Observation.effective[x]
                  Definition

                  The time or time-period the observed value is asserted as being true. For biological subjects - e.g. human patients - this is usually called the "physiologically relevant time". This is usually either the time of the procedure or of specimen collection, but very often the source of the date/time is not known, only the date/time itself.

                  ShortClinically relevant time/time-period for observation
                  Comments

                  At least a date should be present unless this observation is a historical report. For recording imprecise or "fuzzy" times (For example, a blood glucose measurement taken "after breakfast") use the Timing datatype which allow the measurement to be tied to regular life events.

                  Control10..1
                  This element is affected by the following invariants: ele-1
                  TypedateTime, Period, Timing, instant
                  [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                  Is Modifierfalse
                  Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                  Must Supporttrue
                  Obligations
                    ObligationsActor
                    SHALL:populate-if-knownClinical Data Repository
                    SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
                    Summarytrue
                    Requirements

                    Knowing when an observation was deemed true is important to its relevance as well as determining trends.

                    Alternate NamesOccurrence
                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                    52. Observation.performer
                    Definition

                    Who was responsible for asserting the observed value as "true".

                    ShortWho is responsible for the observation
                    Comments

                    References SHALL be a reference to an actual FHIR resource, and SHALL be resolveable (allowing for access control, temporary unavailability, etc.). Resolution can be either by retrieval from the URL, or, where applicable by resource type, by treating an absolute reference as a canonical URL and looking it up in a local registry/repository.

                    Control10..*
                    This element is affected by the following invariants: ele-1
                    TypeReference(Practitioner, Patient, Practitioner, PractitionerRole, Organization, CareTeam, Patient, RelatedPerson)
                    Is Modifierfalse
                    Must Supporttrue
                    Must Support TypesNo must-support rules about the choice of types/profiles
                    Summarytrue
                    Requirements

                    May give a degree of confidence in the observation and also indicates where follow-up questions should be directed.

                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                    ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                    54. Observation.performer.identifier
                    Definition

                    An identifier - identifies some entity uniquely and unambiguously. Typically this is used for business identifiers.


                    An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.

                    ShortAn identifier intended for computationLogical reference, when literal reference is not known
                    Comments

                    When an identifier is provided in place of a reference, any system processing the reference will only be able to resolve the identifier to a reference if it understands the business context in which the identifier is used. Sometimes this is global (e.g. a national identifier) but often it is not. For this reason, none of the useful mechanisms described for working with references (e.g. chaining, includes) are possible, nor should servers be expected to be able resolve the reference. Servers may accept an identifier based reference untouched, resolve it, and/or reject it - see CapabilityStatement.rest.resource.referencePolicy.

                    When both an identifier and a literal reference are provided, the literal reference is preferred. Applications processing the resource are allowed - but not required - to check that the identifier matches the literal reference

                    Applications converting a logical reference to a literal reference may choose to leave the logical reference present, or remove it.

                    Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

                    NoteThis is a business identifier, not a resource identifier (see discussion)
                    Control0..1
                    This element is affected by the following invariants: ele-1
                    TypeIdentifier(UK Professional License, NHS, HCSN and CHI Numbers, Staff Enterprise Number)
                    Is Modifierfalse
                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                    56. Observation.value[x]
                    Definition

                    The information determined as a result of making the observation, if the information has a simple value.

                    ShortActual result
                    Comments

                    An observation may have; 1) a single value here, 2) both a value and a set of related or component values, or 3) only a set of related or component values. If a value is present, the datatype for this element should be determined by Observation.code. A CodeableConcept with just a text would be used instead of a string if the field was usually coded, or if the type associated with the Observation.code defines a coded value. For additional guidance, see the Notes section below.

                    Control0..1
                    This element is affected by the following invariants: ele-1, obs-7
                    TypeChoice of: Quantity, CodeableConcept, string, boolean, integer, Range, Ratio, SampledData, time, dateTime, Period
                    [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                    Is Modifierfalse
                    Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                    Must Supporttrue
                    Must Support TypesNo must-support rules about the choice of types/profiles
                    Obligations
                      ObligationsActor
                      SHALL:populate-if-knownClinical Data Repository
                      SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
                      Summarytrue
                      Requirements

                      An observation exists to have a value, though it might not if it is in error, or if it represents a group of observations.

                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      58. Observation.dataAbsentReason
                      Definition

                      Provides a reason why the expected value in the element Observation.value[x] is missing.

                      ShortWhy the result is missing
                      Comments

                      Null or exceptional values can be represented two ways in FHIR Observations. One way is to simply include them in the value set and represent the exceptions in the value. For example, measurement values for a serology test could be "detected", "not detected", "inconclusive", or "specimen unsatisfactory".

                      The alternate way is to use the value element for actual observations and use the explicit dataAbsentReason element to record exceptional values. For example, the dataAbsentReason code "error" could be used when the measurement was not completed. Note that an observation may only be reported if there are values to report. For example differential cell counts values may be reported only when > 0. Because of these options, use-case agreements are required to interpret general observations for null or exceptional values.

                      Control0..1
                      This element is affected by the following invariants: ele-1, obs-6
                      BindingUnless not suitable, these codes SHALL be taken from DataAbsentReasonhttp://hl7.org/fhir/ValueSet/data-absent-reason
                      (extensible to http://hl7.org/fhir/ValueSet/data-absent-reason)

                      Codes specifying why the result (Observation.value[x]) is missing.

                      TypeCodeableConcept
                      Is Modifierfalse
                      Requirements

                      For many results it is necessary to handle exceptional values in measurements.

                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      60. Observation.component
                      Definition

                      Some observations have multiple component observations. These component observations are expressed as separate code value pairs that share the same attributes. Examples include systolic and diastolic component observations for blood pressure measurement and multiple component observations for genetics observations.

                      ShortComponent results
                      Comments

                      For a discussion on the ways Observations can be assembled in groups together see Notes below.

                      Control0..*
                      This element is affected by the following invariants: ele-1
                      TypeBackboneElement
                      Is Modifierfalse
                      Must Supporttrue
                      Summarytrue
                      Requirements

                      Component observations share the same attributes in the Observation resource as the primary observation and are always treated a part of a single observation (they are not separable). However, the reference range for the primary observation value is not inherited by the component values and is required when appropriate for each component observation.

                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      62. Observation.component.modifierExtension
                      Definition

                      May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

                      Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

                      ShortExtensions that cannot be ignored even if unrecognized
                      Comments

                      There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                      Control0..*
                      This element is affected by the following invariants: ele-1
                      TypeExtension
                      Is Modifiertrue because Modifier extensions are expected to modify the meaning or interpretation of the element that contains them
                      Summarytrue
                      Requirements

                      Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

                      Alternate Namesextensions, user content, modifiers
                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                      ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                      64. Observation.component.code
                      Definition

                      Describes what was observed. Sometimes this is called the observation "code".

                      ShortType of component observation (code / type)
                      Comments

                      All code-value and component.code-component.value pairs need to be taken into account to correctly understand the meaning of the observation.

                      Control1..1
                      This element is affected by the following invariants: ele-1
                      BindingThe codes SHOULD be taken from For example codes, see UK Core Observation Typehttp://hl7.org/fhir/ValueSet/observation-codes
                      (preferred to https://fhir.hl7.org.uk/ValueSet/UKCore-ObservationType)

                      A code from the SNOMED Clinical Terminology UK coding system describing a type of observation


                      Codes identifying names of simple observations.

                      TypeCodeableConcept
                      Is Modifierfalse
                      Summarytrue
                      Requirements

                      Knowing what kind of observation is being made is essential to understanding the observation.

                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      66. Observation.component.dataAbsentReason
                      Definition

                      Provides a reason why the expected value in the element Observation.component.value[x] is missing.

                      ShortWhy the component result is missing
                      Comments

                      "Null" or exceptional values can be represented two ways in FHIR Observations. One way is to simply include them in the value set and represent the exceptions in the value. For example, measurement values for a serology test could be "detected", "not detected", "inconclusive", or "test not done".

                      The alternate way is to use the value element for actual observations and use the explicit dataAbsentReason element to record exceptional values. For example, the dataAbsentReason code "error" could be used when the measurement was not completed. Because of these options, use-case agreements are required to interpret general observations for exceptional values.

                      Control0..1
                      This element is affected by the following invariants: ele-1, obs-6
                      BindingUnless not suitable, these codes SHALL be taken from DataAbsentReasonhttp://hl7.org/fhir/ValueSet/data-absent-reason
                      (extensible to http://hl7.org/fhir/ValueSet/data-absent-reason)

                      Codes specifying why the result (Observation.value[x]) is missing.

                      TypeCodeableConcept
                      Is Modifierfalse
                      Requirements

                      For many results it is necessary to handle exceptional values in measurements.

                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))

                      Guidance on how to interpret the contents of this table can be found here

                      0. Observation
                      Definition

                      Measurements and simple assertions made about a patient, device or other subject.

                      ShortMeasurements and simple assertions
                      Comments

                      Used for simple observations such as device measurements, laboratory atomic results, vital signs, height, weight, smoking status, comments, etc. Other resources are used to provide context for observations such as laboratory reports, etc.

                      Control0..*
                      Alternate NamesVital Signs, Measurement, Results, Tests
                      Invariantsdom-2: If the resource is contained in another resource, it SHALL NOT contain nested Resources (contained.contained.empty())
                      dom-4: If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated (contained.meta.versionId.empty() and contained.meta.lastUpdated.empty())
                      dom-3: If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource (contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().as(canonical) | %resource.descendants().as(uri) | %resource.descendants().as(url))) or descendants().where(reference = '#').exists() or descendants().where(as(canonical) = '#').exists() or descendants().where(as(canonical) = '#').exists()).not()).trace('unmatched', id).empty())
                      dom-6: A resource should have narrative for robust management (text.`div`.exists())
                      dom-5: If a resource is contained in another resource, it SHALL NOT have a security label (contained.meta.security.empty())
                      obs-7: If Observation.code is the same as an Observation.component.code then the value element associated with the code SHALL NOT be present (value.empty() or component.code.where(coding.intersect(%resource.code.coding).exists()).empty())
                      obs-6: dataAbsentReason SHALL only be present if Observation.value[x] is not present (dataAbsentReason.empty() or value.empty())
                      2. Observation.id
                      Definition

                      The logical id of the resource, as used in the URL for the resource. Once assigned, this value never changes.

                      ShortLogical id of this artifact
                      Comments

                      The only time that a resource does not have an id is when it is being submitted to the server using a create operation.

                      Control0..1
                      Typeid
                      Summarytrue
                      4. Observation.meta
                      Definition

                      The metadata about the resource. This is content that is maintained by the infrastructure. Changes to the content might not always be associated with version changes to the resource.

                      ShortMetadata about the resource
                      Control0..1
                      This element is affected by the following invariants: ele-1
                      TypeMeta
                      Summarytrue
                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      6. Observation.implicitRules
                      Definition

                      A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content. Often, this is a reference to an implementation guide that defines the special rules along with other profiles etc.

                      ShortA set of rules under which this content was created
                      Comments

                      Asserting this rule set restricts the content to be only understood by a limited set of trading partners. This inherently limits the usefulness of the data in the long term. However, the existing health eco-system is highly fractured, and not yet ready to define, collect, and exchange data in a generally computable sense. Wherever possible, implementers and/or specification writers should avoid using this element. Often, when used, the URL is a reference to an implementation guide that defines these special rules as part of it's narrative along with other profiles, value sets, etc.

                      Control0..1
                      This element is affected by the following invariants: ele-1
                      Typeuri
                      Is Modifiertrue because This element is labeled as a modifier because the implicit rules may provide additional knowledge about the resource that modifies it's meaning or interpretation
                      Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                      Summarytrue
                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      8. Observation.language
                      Definition

                      The base language in which the resource is written.

                      ShortLanguage of the resource content
                      Comments

                      Language is provided to support indexing and accessibility (typically, services such as text to speech use the language tag). The html language tag in the narrative applies to the narrative. The language tag on the resource may be used to specify the language of other presentations generated from the data in the resource. Not all the content has to be in the base language. The Resource.language should not be assumed to apply to the narrative automatically. If a language is specified, it should it also be specified on the div element in the html (see rules in HTML5 for information about the relationship between xml:lang and the html lang attribute).

                      Control0..1
                      This element is affected by the following invariants: ele-1
                      BindingThe codes SHOULD be taken from CommonLanguages
                      (preferred to http://hl7.org/fhir/ValueSet/languages)

                      A human language.

                      Additional BindingsPurpose
                      AllLanguagesMax Binding
                      Typecode
                      Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      10. Observation.text
                      Definition

                      A human-readable narrative that contains a summary of the resource and can be used to represent the content of the resource to a human. The narrative need not encode all the structured data, but is required to contain sufficient detail to make it "clinically safe" for a human to just read the narrative. Resource definitions may define what content should be represented in the narrative to ensure clinical safety.

                      ShortText summary of the resource, for human interpretation
                      Comments

                      Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded information is added later.

                      Control0..1
                      This element is affected by the following invariants: ele-1
                      TypeNarrative
                      Alternate Namesnarrative, html, xhtml, display
                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      12. Observation.contained
                      Definition

                      These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, and nor can they have their own independent transaction scope.

                      ShortContained, inline Resources
                      Comments

                      This should never be done when the content can be identified properly, as once identification is lost, it is extremely difficult (and context dependent) to restore it again. Contained resources may have profiles and tags In their meta elements, but SHALL NOT have security labels.

                      Control0..*
                      TypeResource
                      Alternate Namesinline resources, anonymous resources, contained resources
                      14. Observation.extension
                      Definition

                      May be used to represent additional information that is not part of the basic definition of the resource. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                      ShortAdditional content defined by implementations
                      Comments

                      There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                      Control0..*
                      This element is affected by the following invariants: ele-1
                      TypeExtension
                      Standard StatusNormative (from Normative)
                      Alternate Namesextensions, user content
                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                      ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                      SlicingThis element introduces a set of slices on Observation.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                      • value @ url
                      • 16. Observation.extension:triggeredByR5
                        Slice NametriggeredByR5
                        Definition

                        Identifies the observation(s) that triggered the performance of this observation.

                        ShortTriggering observation(s). This is a R5 backport.
                        Comments

                        There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                        Control0..*
                        This element is affected by the following invariants: ele-1
                        TypeExtension(Extension UK Core Observation Triggered By) (Complex Extension)
                        Standard StatusNormative (from Normative)
                        Alternate Namesextensions, user content
                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                        ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                        18. Observation.extension:triggeredByR5.id
                        Definition

                        Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                        ShortUnique id for inter-element referencing
                        Control0..1
                        Typestring
                        XML FormatIn the XML format, this property is represented as an attribute.
                        20. Observation.extension:triggeredByR5.extension
                        Definition

                        May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                        ShortAdditional content defined by implementations
                        Comments

                        There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                        Control2..*
                        This element is affected by the following invariants: ele-1
                        TypeExtension
                        Standard StatusNormative (from Normative)
                        Alternate Namesextensions, user content
                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                        ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                        SlicingThis element introduces a set of slices on Observation.extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                        • value @ url
                        • 22. Observation.extension:triggeredByR5.extension:observation
                          Slice Nameobservation
                          Definition

                          Reference to the triggering observation.

                          ShortTriggering observation
                          Comments

                          There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                          Control1..1
                          This element is affected by the following invariants: ele-1
                          TypeExtension
                          Standard StatusNormative (from Normative)
                          Alternate Namesextensions, user content
                          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                          ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                          24. Observation.extension:triggeredByR5.extension:observation.id
                          Definition

                          Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                          ShortUnique id for inter-element referencing
                          Control0..1
                          Typestring
                          XML FormatIn the XML format, this property is represented as an attribute.
                          26. Observation.extension:triggeredByR5.extension:observation.extension
                          Definition

                          May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                          ShortAdditional content defined by implementations
                          Comments

                          There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                          Control0..*
                          This element is affected by the following invariants: ele-1
                          TypeExtension
                          Standard StatusNormative (from Normative)
                          Alternate Namesextensions, user content
                          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                          ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                          SlicingThis element introduces a set of slices on Observation.extension.extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                          • value @ url
                          • 28. Observation.extension:triggeredByR5.extension:observation.url
                            Definition

                            Source of the definition for the extension code - a logical name or a URL.

                            Shortidentifies the meaning of the extension
                            Comments

                            The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

                            Control1..1
                            Typeuri
                            XML FormatIn the XML format, this property is represented as an attribute.
                            Fixed Valueobservation
                            30. Observation.extension:triggeredByR5.extension:observation.value[x]
                            Definition

                            A reference to the triggering observation.

                            ShortTriggering observation.
                            Control1..1
                            This element is affected by the following invariants: ele-1
                            TypeReference(Observation)
                            [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                            Standard StatusNormative (from Normative)
                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                            32. Observation.extension:triggeredByR5.extension:type
                            Slice Nametype
                            Definition

                            The type of trigger. Reflex | Repeat | Re-run.

                            Shortreflex | repeat | re-run
                            Comments

                            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                            Control1..1
                            This element is affected by the following invariants: ele-1
                            BindingThe codes SHALL be taken from observation-triggeredbytype
                            (required to http://hl7.org/fhir/ValueSet/observation-triggeredbytype)
                            TypeExtension
                            Standard StatusNormative (from Normative)
                            Alternate Namesextensions, user content
                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                            34. Observation.extension:triggeredByR5.extension:type.id
                            Definition

                            Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                            ShortUnique id for inter-element referencing
                            Control0..1
                            Typestring
                            XML FormatIn the XML format, this property is represented as an attribute.
                            36. Observation.extension:triggeredByR5.extension:type.extension
                            Definition

                            May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                            ShortAdditional content defined by implementations
                            Comments

                            There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                            Control0..*
                            This element is affected by the following invariants: ele-1
                            TypeExtension
                            Standard StatusNormative (from Normative)
                            Alternate Namesextensions, user content
                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                            ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                            SlicingThis element introduces a set of slices on Observation.extension.extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                            • value @ url
                            • 38. Observation.extension:triggeredByR5.extension:type.url
                              Definition

                              Source of the definition for the extension code - a logical name or a URL.

                              Shortidentifies the meaning of the extension
                              Comments

                              The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

                              Control1..1
                              Typeuri
                              XML FormatIn the XML format, this property is represented as an attribute.
                              Fixed Valuetype
                              40. Observation.extension:triggeredByR5.extension:type.value[x]
                              Definition

                              The type of trigger. Reflex | Repeat | Re-run

                              ShortThe type of trigger. Reflex | Repeat | Re-run
                              Control1..1
                              This element is affected by the following invariants: ele-1
                              Typecode
                              [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                              Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                              Standard StatusNormative (from Normative)
                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                              42. Observation.extension:triggeredByR5.extension:reason
                              Slice Namereason
                              Definition

                              Provides the reason why this observation was performed as a result of the observation(s) referenced.

                              ShortReason that the observation was triggered
                              Comments

                              There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                              Control0..1
                              This element is affected by the following invariants: ele-1
                              TypeExtension
                              Standard StatusNormative (from Normative)
                              Alternate Namesextensions, user content
                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                              ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                              44. Observation.extension:triggeredByR5.extension:reason.id
                              Definition

                              Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                              ShortUnique id for inter-element referencing
                              Control0..1
                              Typestring
                              XML FormatIn the XML format, this property is represented as an attribute.
                              46. Observation.extension:triggeredByR5.extension:reason.extension
                              Definition

                              May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                              ShortAdditional content defined by implementations
                              Comments

                              There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                              Control0..*
                              This element is affected by the following invariants: ele-1
                              TypeExtension
                              Standard StatusNormative (from Normative)
                              Alternate Namesextensions, user content
                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                              ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                              SlicingThis element introduces a set of slices on Observation.extension.extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                              • value @ url
                              • 48. Observation.extension:triggeredByR5.extension:reason.url
                                Definition

                                Source of the definition for the extension code - a logical name or a URL.

                                Shortidentifies the meaning of the extension
                                Comments

                                The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

                                Control1..1
                                Typeuri
                                XML FormatIn the XML format, this property is represented as an attribute.
                                Fixed Valuereason
                                50. Observation.extension:triggeredByR5.extension:reason.value[x]
                                Definition

                                Provides the reason why this observation was performed as a result of the observation referenced.

                                ShortReason that the observation was triggered.
                                Control1..1
                                This element is affected by the following invariants: ele-1
                                Typestring
                                [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                                Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                Standard StatusNormative (from Normative)
                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                52. Observation.extension:triggeredByR5.url
                                Definition

                                Source of the definition for the extension code - a logical name or a URL.

                                Shortidentifies the meaning of the extension
                                Comments

                                The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

                                Control1..1
                                Typeuri
                                XML FormatIn the XML format, this property is represented as an attribute.
                                Fixed Valuehttp://hl7.org/fhir/5.0/StructureDefinition/extension-Observation.triggeredBy
                                54. Observation.extension:triggeredByR5.value[x]
                                Definition

                                Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

                                ShortValue of extension
                                Control0..0
                                This element is affected by the following invariants: ele-1
                                TypeChoice of: base64Binary, boolean, canonical, code, date, dateTime, decimal, id, instant, integer, markdown, oid, positiveInt, string, time, unsignedInt, uri, url, uuid, Address, Age, Annotation, Attachment, CodeableConcept, Coding, ContactPoint, Count, Distance, Duration, HumanName, Identifier, Money, Period, Quantity, Range, Ratio, Reference, SampledData, Signature, Timing, ContactDetail, Contributor, DataRequirement, Expression, ParameterDefinition, RelatedArtifact, TriggerDefinition, UsageContext, Dosage, Meta
                                Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                Standard StatusNormative (from Normative)
                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                56. Observation.extension:bodyStructureR5
                                Slice NamebodyStructureR5
                                Definition

                                Indicates the body structure on the subject's body where the observation was made (i.e. the target site).

                                ShortObserved body structure. This is a R5 backport.
                                Comments

                                There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                Control0..1
                                This element is affected by the following invariants: ele-1
                                TypeExtension(Extension UK Core Observation Body Structure) (Extension Type: Reference(BodyStructure))
                                Standard StatusNormative (from Normative)
                                Alternate Namesextensions, user content
                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                58. Observation.modifierExtension
                                Definition

                                May be used to represent additional information that is not part of the basic definition of the resource and that modifies the understanding of the element that contains it and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

                                Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

                                ShortExtensions that cannot be ignored
                                Comments

                                There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                Control0..*
                                This element is affected by the following invariants: ele-1
                                TypeExtension
                                Is Modifiertrue because Modifier extensions are expected to modify the meaning or interpretation of the resource that contains them
                                Standard StatusNormative (from Normative)
                                Requirements

                                Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

                                Alternate Namesextensions, user content
                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                SlicingThis element introduces a set of slices on Observation.modifierExtension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                                • value @ url
                                • 60. Observation.identifier
                                  Definition

                                  A unique identifier assigned to this observation.

                                  ShortBusiness Identifier for observation
                                  NoteThis is a business identifier, not a resource identifier (see discussion)
                                  Control1..*
                                  This element is affected by the following invariants: ele-1
                                  TypeIdentifier
                                  Must Supporttrue
                                  Summarytrue
                                  Requirements

                                  Allows observations to be distinguished and referenced.

                                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                  SlicingThis element introduces a set of slices on Observation.identifier. The slices areUnordered and Closed, and can be differentiated using the following discriminators:
                                  • pattern @ system
                                  • 62. Observation.identifier:CommonResourceIdentifiers
                                    Slice NameCommonResourceIdentifiers
                                    Definition

                                    An identifier - identifies some entity uniquely and unambiguously. Typically this is used for business identifiers.

                                    ShortCommon Resource Identifiers
                                    NoteThis is a business identifier, not a resource identifier (see discussion)
                                    Control0..*
                                    This element is affected by the following invariants: ele-1
                                    TypeIdentifier(Common Resource Identifiers)
                                    Is Modifierfalse
                                    Requirements

                                    Allows observations to be distinguished and referenced.

                                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                    64. Observation.basedOn
                                    Definition

                                    A plan, proposal or order that is fulfilled in whole or in part by this event. For example, a MedicationRequest may require a patient to have laboratory test performed before it is dispensed.

                                    ShortFulfills plan, proposal or order
                                    Comments

                                    References SHALL be a reference to an actual FHIR resource, and SHALL be resolveable (allowing for access control, temporary unavailability, etc.). Resolution can be either by retrieval from the URL, or, where applicable by resource type, by treating an absolute reference as a canonical URL and looking it up in a local registry/repository.

                                    Control0..*
                                    This element is affected by the following invariants: ele-1
                                    TypeReference(CarePlan, DeviceRequest, ImmunizationRecommendation, MedicationRequest, NutritionOrder, ServiceRequest)
                                    Summarytrue
                                    Requirements

                                    Allows tracing of authorization for the event and tracking whether proposals/recommendations were acted upon.

                                    Alternate NamesFulfills
                                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                    ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                    66. Observation.partOf
                                    Definition

                                    A larger event of which this particular Observation is a component or step. For example, an observation as part of a procedure.

                                    ShortPart of referenced event
                                    Comments

                                    To link an Observation to an Encounter use encounter. See the Notes below for guidance on referencing another Observation.

                                    Control0..*
                                    This element is affected by the following invariants: ele-1
                                    TypeReference(MedicationAdministration, MedicationDispense, MedicationStatement, Procedure, Immunization, ImagingStudy)
                                    Summarytrue
                                    Alternate NamesContainer
                                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                    ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                    68. Observation.status
                                    Definition

                                    The status of the result value.

                                    Shortregistered | preliminary | final | amended +
                                    Comments

                                    This element is labeled as a modifier because the status contains codes that mark the resource as not currently valid.

                                    Control1..1
                                    This element is affected by the following invariants: ele-1
                                    BindingThe codes SHALL be taken from ObservationStatus
                                    (required to http://hl7.org/fhir/ValueSet/observation-status|4.0.1)

                                    Codes providing the status of an observation.

                                    Typecode
                                    Is Modifiertrue because This element is labeled as a modifier because it is a status element that contains status entered-in-error which means that the resource should not be treated as valid
                                    Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                    Must Supporttrue
                                    Summarytrue
                                    Requirements

                                    Need to track the status of individual results. Some results are finalized before the whole report is finalized.

                                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                    70. Observation.category
                                    Definition

                                    A code that classifies the general type of observation being made.

                                    ShortClassification of type of observation
                                    Comments

                                    In addition to the required category valueset, this element allows various categorization schemes based on the owner’s definition of the category and effectively multiple categories can be used at once. The level of granularity is defined by the category concepts in the value set.

                                    Control0..*
                                    This element is affected by the following invariants: ele-1
                                    BindingThe codes SHOULD be taken from ObservationCategoryCodes
                                    (preferred to http://hl7.org/fhir/ValueSet/observation-category)

                                    Codes for high level observation categories.

                                    TypeCodeableConcept
                                    Must Supporttrue
                                    Requirements

                                    Used for filtering what observations are retrieved and displayed.

                                    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                    72. Observation.code
                                    Definition

                                    Describes what was observed. Sometimes this is called the observation "name".

                                    ShortType of observation (code / type)
                                    Comments

                                    All code-value and, if present, component.code-component.value pairs need to be taken into account to correctly understand the meaning of the observation.

                                    Control1..1
                                    This element is affected by the following invariants: ele-1
                                    BindingThe codes SHOULD be taken from UK Core Observation Type
                                    (preferred to https://fhir.hl7.org.uk/ValueSet/UKCore-ObservationType)

                                    A code from the SNOMED Clinical Terminology UK coding system describing a type of observation

                                    TypeCodeableConcept
                                    Must Supporttrue
                                    Obligations
                                      ObligationsActor
                                      SHALL:populate-if-knownClinical Data Repository
                                      SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
                                      Summarytrue
                                      Requirements

                                      Knowing what kind of observation is being made is essential to understanding the observation.

                                      Alternate NamesName
                                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                      74. Observation.subject
                                      Definition

                                      The patient, or group of patients, location, or device this observation is about and into whose record the observation is placed. If the actual focus of the observation is different from the subject (or a sample of, part, or region of the subject), the focus element or the code itself specifies the actual focus of the observation.

                                      ShortWho and/or what the observation is about
                                      Comments

                                      One would expect this element to be a cardinality of 1..1. The only circumstance in which the subject can be missing is when the observation is made by a device that does not know the patient. In this case, the observation SHALL be matched to a patient through some context/channel matching technique, and at this point, the observation should be updated.

                                      Control0..1
                                      This element is affected by the following invariants: ele-1
                                      TypeReference(Patient, Group, Device, Location)
                                      Must Supporttrue
                                      Must Support TypesNo must-support rules about the choice of types/profiles
                                      Summarytrue
                                      Requirements

                                      Observations have no value if you don't know who or what they're about.

                                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                      ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                      76. Observation.subject.id
                                      Definition

                                      Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                                      ShortUnique id for inter-element referencing
                                      Control0..1
                                      Typestring
                                      Is Modifierfalse
                                      XML FormatIn the XML format, this property is represented as an attribute.
                                      Summaryfalse
                                      78. Observation.subject.extension
                                      Definition

                                      May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                                      ShortAdditional content defined by implementations
                                      Comments

                                      There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                      Control0..*
                                      TypeExtension
                                      Is Modifierfalse
                                      Summaryfalse
                                      Alternate Namesextensions, user content
                                      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                      ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                      SlicingThis element introduces a set of slices on Observation.subject.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                                      • value @ url
                                      • 80. Observation.subject.reference
                                        Definition

                                        A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

                                        ShortLiteral reference, Relative, internal or absolute URL
                                        Comments

                                        Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "/[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

                                        Control1..1
                                        This element is affected by the following invariants: ref-1
                                        Typestring
                                        Is Modifierfalse
                                        Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                        Must Supporttrue
                                        Summarytrue
                                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                        82. Observation.subject.type
                                        Definition

                                        The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

                                        The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

                                        ShortType the reference refers to (e.g. "Patient")
                                        Comments

                                        This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

                                        Control0..1
                                        BindingUnless not suitable, these codes SHALL be taken from ResourceType
                                        (extensible to http://hl7.org/fhir/ValueSet/resource-types)

                                        Aa resource (or, for logical models, the URI of the logical model).

                                        Typeuri
                                        Is Modifierfalse
                                        Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                        Summarytrue
                                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                        84. Observation.subject.identifier
                                        Definition

                                        An identifier - identifies some entity uniquely and unambiguously. Typically this is used for business identifiers.

                                        ShortAn identifier intended for computation
                                        Comments

                                        When an identifier is provided in place of a reference, any system processing the reference will only be able to resolve the identifier to a reference if it understands the business context in which the identifier is used. Sometimes this is global (e.g. a national identifier) but often it is not. For this reason, none of the useful mechanisms described for working with references (e.g. chaining, includes) are possible, nor should servers be expected to be able resolve the reference. Servers may accept an identifier based reference untouched, resolve it, and/or reject it - see CapabilityStatement.rest.resource.referencePolicy.

                                        When both an identifier and a literal reference are provided, the literal reference is preferred. Applications processing the resource are allowed - but not required - to check that the identifier matches the literal reference

                                        Applications converting a logical reference to a literal reference may choose to leave the logical reference present, or remove it.

                                        Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

                                        NoteThis is a business identifier, not a resource identifier (see discussion)
                                        Control0..1
                                        This element is affected by the following invariants: ele-1
                                        TypeIdentifier(NHS, HCSN and CHI Numbers)
                                        Is Modifierfalse
                                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                        86. Observation.subject.display
                                        Definition

                                        Plain text narrative that identifies the resource in addition to the resource reference.

                                        ShortText alternative for the resource
                                        Comments

                                        This is generally not the same as the Resource.text of the referenced resource. The purpose is to identify what's being referenced, not to fully describe it.

                                        Control0..1
                                        Typestring
                                        Is Modifierfalse
                                        Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                        Summarytrue
                                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                        88. Observation.focus
                                        Definition

                                        The actual focus of an observation when it is not the patient of record representing something or someone associated with the patient such as a spouse, parent, fetus, or donor. For example, fetus observations in a mother's record. The focus of an observation could also be an existing condition, an intervention, the subject's diet, another observation of the subject, or a body structure such as tumor or implanted device. An example use case would be using the Observation resource to capture whether the mother is trained to change her child's tracheostomy tube. In this example, the child is the patient of record and the mother is the focus.

                                        ShortWhat the observation is about, when it is not about the subject of record
                                        Comments

                                        Typically, an observation is made about the subject - a patient, or group of patients, location, or device - and the distinction between the subject and what is directly measured for an observation is specified in the observation code itself ( e.g., "Blood Glucose") and does not need to be represented separately using this element. Use specimen if a reference to a specimen is required. If a code is required instead of a resource use either bodysite for bodysites or the standard extension focusCode.

                                        Control0..*
                                        This element is affected by the following invariants: ele-1
                                        TypeReference(Resource)
                                        Summarytrue
                                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                        ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                        90. Observation.encounter
                                        Definition

                                        The healthcare event (e.g. a patient and healthcare provider interaction) during which this observation is made.

                                        ShortHealthcare event during which this observation is made
                                        Comments

                                        This will typically be the encounter the event occurred within, but some events may be initiated prior to or after the official completion of an encounter but still be tied to the context of the encounter (e.g. pre-admission laboratory tests).

                                        Control0..1
                                        This element is affected by the following invariants: ele-1
                                        TypeReference(Encounter)
                                        Summarytrue
                                        Requirements

                                        For some observations it may be important to know the link between an observation and a particular encounter.

                                        Alternate NamesContext
                                        Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                        ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                        92. Observation.effective[x]
                                        Definition

                                        The time or time-period the observed value is asserted as being true. For biological subjects - e.g. human patients - this is usually called the "physiologically relevant time". This is usually either the time of the procedure or of specimen collection, but very often the source of the date/time is not known, only the date/time itself.

                                        ShortClinically relevant time/time-period for observation
                                        Comments

                                        At least a date should be present unless this observation is a historical report. For recording imprecise or "fuzzy" times (For example, a blood glucose measurement taken "after breakfast") use the Timing datatype which allow the measurement to be tied to regular life events.

                                        Control1..1
                                        This element is affected by the following invariants: ele-1
                                        TypedateTime
                                        [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                                        Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                        Must Supporttrue
                                        Obligations
                                          ObligationsActor
                                          SHALL:populate-if-knownClinical Data Repository
                                          SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
                                          Summarytrue
                                          Requirements

                                          Knowing when an observation was deemed true is important to its relevance as well as determining trends.

                                          Alternate NamesOccurrence
                                          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                          94. Observation.issued
                                          Definition

                                          The date and time this version of the observation was made available to providers, typically after the results have been reviewed and verified.

                                          ShortDate/Time this version was made available
                                          Comments

                                          For Observations that don’t require review and verification, it may be the same as the lastUpdated time of the resource itself. For Observations that do require review and verification for certain updates, it might not be the same as the lastUpdated time of the resource itself due to a non-clinically significant update that doesn’t require the new version to be reviewed and verified again.

                                          Control0..1
                                          This element is affected by the following invariants: ele-1
                                          Typeinstant
                                          Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                          Summarytrue
                                          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                          96. Observation.performer
                                          Definition

                                          Who was responsible for asserting the observed value as "true".

                                          ShortWho is responsible for the observation
                                          Comments

                                          References SHALL be a reference to an actual FHIR resource, and SHALL be resolveable (allowing for access control, temporary unavailability, etc.). Resolution can be either by retrieval from the URL, or, where applicable by resource type, by treating an absolute reference as a canonical URL and looking it up in a local registry/repository.

                                          Control1..*
                                          This element is affected by the following invariants: ele-1
                                          TypeReference(Practitioner, Patient)
                                          Must Supporttrue
                                          Must Support TypesNo must-support rules about the choice of types/profiles
                                          Summarytrue
                                          Requirements

                                          May give a degree of confidence in the observation and also indicates where follow-up questions should be directed.

                                          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                          ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                          98. Observation.performer.id
                                          Definition

                                          Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                                          ShortUnique id for inter-element referencing
                                          Control0..1
                                          Typestring
                                          Is Modifierfalse
                                          XML FormatIn the XML format, this property is represented as an attribute.
                                          Summaryfalse
                                          100. Observation.performer.extension
                                          Definition

                                          May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                                          ShortAdditional content defined by implementations
                                          Comments

                                          There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                          Control0..*
                                          TypeExtension
                                          Is Modifierfalse
                                          Summaryfalse
                                          Alternate Namesextensions, user content
                                          Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                          ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                          SlicingThis element introduces a set of slices on Observation.performer.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                                          • value @ url
                                          • 102. Observation.performer.reference
                                            Definition

                                            A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

                                            ShortLiteral reference, Relative, internal or absolute URL
                                            Comments

                                            Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "/[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

                                            Control0..1
                                            This element is affected by the following invariants: ref-1
                                            Typestring
                                            Is Modifierfalse
                                            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                            Summarytrue
                                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                            104. Observation.performer.type
                                            Definition

                                            The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

                                            The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

                                            ShortType the reference refers to (e.g. "Patient")
                                            Comments

                                            This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

                                            Control0..1
                                            BindingUnless not suitable, these codes SHALL be taken from ResourceType
                                            (extensible to http://hl7.org/fhir/ValueSet/resource-types)

                                            Aa resource (or, for logical models, the URI of the logical model).

                                            Typeuri
                                            Is Modifierfalse
                                            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                            Summarytrue
                                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                            106. Observation.performer.identifier
                                            Definition

                                            An identifier - identifies some entity uniquely and unambiguously. Typically this is used for business identifiers.

                                            ShortAn identifier intended for computation
                                            Comments

                                            When an identifier is provided in place of a reference, any system processing the reference will only be able to resolve the identifier to a reference if it understands the business context in which the identifier is used. Sometimes this is global (e.g. a national identifier) but often it is not. For this reason, none of the useful mechanisms described for working with references (e.g. chaining, includes) are possible, nor should servers be expected to be able resolve the reference. Servers may accept an identifier based reference untouched, resolve it, and/or reject it - see CapabilityStatement.rest.resource.referencePolicy.

                                            When both an identifier and a literal reference are provided, the literal reference is preferred. Applications processing the resource are allowed - but not required - to check that the identifier matches the literal reference

                                            Applications converting a logical reference to a literal reference may choose to leave the logical reference present, or remove it.

                                            Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

                                            NoteThis is a business identifier, not a resource identifier (see discussion)
                                            Control0..1
                                            This element is affected by the following invariants: ele-1
                                            TypeIdentifier(UK Professional License, NHS, HCSN and CHI Numbers, Staff Enterprise Number)
                                            Is Modifierfalse
                                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                            108. Observation.performer.display
                                            Definition

                                            Plain text narrative that identifies the resource in addition to the resource reference.

                                            ShortText alternative for the resource
                                            Comments

                                            This is generally not the same as the Resource.text of the referenced resource. The purpose is to identify what's being referenced, not to fully describe it.

                                            Control0..1
                                            Typestring
                                            Is Modifierfalse
                                            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                            Summarytrue
                                            Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                            110. Observation.value[x]
                                            Definition

                                            The information determined as a result of making the observation, if the information has a simple value.

                                            ShortActual result
                                            Comments

                                            An observation may have; 1) a single value here, 2) both a value and a set of related or component values, or 3) only a set of related or component values. If a value is present, the datatype for this element should be determined by Observation.code. A CodeableConcept with just a text would be used instead of a string if the field was usually coded, or if the type associated with the Observation.code defines a coded value. For additional guidance, see the Notes section below.

                                            Control0..1
                                            This element is affected by the following invariants: ele-1, obs-7
                                            TypeChoice of: Quantity, CodeableConcept, string, boolean, integer, Range, Ratio, SampledData, time, dateTime, Period
                                            [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                                            Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                            Must Supporttrue
                                            Must Support TypesNo must-support rules about the choice of types/profiles
                                            Obligations
                                              ObligationsActor
                                              SHALL:populate-if-knownClinical Data Repository
                                              SHALL:populate-if-knownhttps://fhir.virtually.healthcare/ActorDefinition/ClinicalDataService
                                              Summarytrue
                                              Requirements

                                              An observation exists to have a value, though it might not if it is in error, or if it represents a group of observations.

                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              112. Observation.dataAbsentReason
                                              Definition

                                              Provides a reason why the expected value in the element Observation.value[x] is missing.

                                              ShortWhy the result is missing
                                              Comments

                                              Null or exceptional values can be represented two ways in FHIR Observations. One way is to simply include them in the value set and represent the exceptions in the value. For example, measurement values for a serology test could be "detected", "not detected", "inconclusive", or "specimen unsatisfactory".

                                              The alternate way is to use the value element for actual observations and use the explicit dataAbsentReason element to record exceptional values. For example, the dataAbsentReason code "error" could be used when the measurement was not completed. Note that an observation may only be reported if there are values to report. For example differential cell counts values may be reported only when > 0. Because of these options, use-case agreements are required to interpret general observations for null or exceptional values.

                                              Control0..1
                                              This element is affected by the following invariants: ele-1, obs-6
                                              BindingUnless not suitable, these codes SHALL be taken from DataAbsentReason
                                              (extensible to http://hl7.org/fhir/ValueSet/data-absent-reason)

                                              Codes specifying why the result (Observation.value[x]) is missing.

                                              TypeCodeableConcept
                                              Requirements

                                              For many results it is necessary to handle exceptional values in measurements.

                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              114. Observation.interpretation
                                              Definition

                                              A categorical assessment of an observation value. For example, high, low, normal.

                                              ShortHigh, low, normal, etc.
                                              Comments

                                              Historically used for laboratory results (known as 'abnormal flag' ), its use extends to other use cases where coded interpretations are relevant. Often reported as one or more simple compact codes this element is often placed adjacent to the result value in reports and flow sheets to signal the meaning/normalcy status of the result.

                                              Control0..*
                                              This element is affected by the following invariants: ele-1
                                              BindingUnless not suitable, these codes SHALL be taken from ObservationInterpretationCodes
                                              (extensible to http://hl7.org/fhir/ValueSet/observation-interpretation)

                                              Codes identifying interpretations of observations.

                                              TypeCodeableConcept
                                              Requirements

                                              For some results, particularly numeric results, an interpretation is necessary to fully understand the significance of a result.

                                              Alternate NamesAbnormal Flag
                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              116. Observation.note
                                              Definition

                                              Comments about the observation or the results.

                                              ShortComments about the observation
                                              Comments

                                              May include general statements about the observation, or statements about significant, unexpected or unreliable results values, or information about its source when relevant to its interpretation.

                                              Control0..*
                                              This element is affected by the following invariants: ele-1
                                              TypeAnnotation
                                              Requirements

                                              Need to be able to provide free text additional information.

                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              118. Observation.bodySite
                                              Definition

                                              Indicates the site on the subject's body where the observation was made (i.e. the target site).

                                              ShortObserved body part
                                              Comments

                                              Only used if not implicit in code found in Observation.code. In many systems, this may be represented as a related observation instead of an inline component.

                                              If the use case requires BodySite to be handled as a separate resource (e.g. to identify and track separately) then use the standard extension bodySite.

                                              Control0..1
                                              This element is affected by the following invariants: ele-1
                                              BindingThe codes SHOULD be taken from SNOMEDCTBodyStructures
                                              (preferred to http://hl7.org/fhir/ValueSet/body-site)

                                              Codes describing anatomical locations. May include laterality.

                                              TypeCodeableConcept
                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              120. Observation.method
                                              Definition

                                              Indicates the mechanism used to perform the observation.

                                              ShortHow it was done
                                              Comments

                                              Only used if not implicit in code for Observation.code.

                                              Control0..1
                                              This element is affected by the following invariants: ele-1
                                              BindingThe codes SHOULD be taken from ObservationMethods
                                              (preferred to http://hl7.org/fhir/ValueSet/observation-methods)

                                              Methods for simple observations.

                                              TypeCodeableConcept
                                              Requirements

                                              In some cases, method can impact results and is thus used for determining whether results can be compared or determining significance of results.

                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              122. Observation.specimen
                                              Definition

                                              The specimen that was used when this observation was made.

                                              ShortSpecimen used for this observation
                                              Comments

                                              Should only be used if not implicit in code found in Observation.code. Observations are not made on specimens themselves; they are made on a subject, but in many cases by the means of a specimen. Note that although specimens are often involved, they are not always tracked and reported explicitly. Also note that observation resources may be used in contexts that track the specimen explicitly (e.g. Diagnostic Report).

                                              Control0..1
                                              This element is affected by the following invariants: ele-1
                                              TypeReference(Specimen)
                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                              124. Observation.device
                                              Definition

                                              The device used to generate the observation data.

                                              Short(Measurement) Device
                                              Comments

                                              Note that this is not meant to represent a device involved in the transmission of the result, e.g., a gateway. Such devices may be documented using the Provenance resource where relevant.

                                              Control0..1
                                              This element is affected by the following invariants: ele-1
                                              TypeReference(Device, DeviceMetric)
                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                              126. Observation.referenceRange
                                              Definition

                                              Guidance on how to interpret the value by comparison to a normal or recommended range. Multiple reference ranges are interpreted as an "OR". In other words, to represent two distinct target populations, two referenceRange elements would be used.

                                              ShortProvides guide for interpretation
                                              Comments

                                              Most observations only have one generic reference range. Systems MAY choose to restrict to only supplying the relevant reference range based on knowledge about the patient (e.g., specific to the patient's age, gender, weight and other factors), but this might not be possible or appropriate. Whenever more than one reference range is supplied, the differences between them SHOULD be provided in the reference range and/or age properties.

                                              Control0..*
                                              This element is affected by the following invariants: ele-1
                                              TypeBackboneElement
                                              Requirements

                                              Knowing what values are considered "normal" can help evaluate the significance of a particular result. Need to be able to provide multiple reference ranges for different contexts.

                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              obs-3: Must have at least a low or a high or text (low.exists() or high.exists() or text.exists())
                                              128. Observation.referenceRange.id
                                              Definition

                                              Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                                              ShortUnique id for inter-element referencing
                                              Control0..1
                                              Typestring
                                              XML FormatIn the XML format, this property is represented as an attribute.
                                              130. Observation.referenceRange.extension
                                              Definition

                                              May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                                              ShortAdditional content defined by implementations
                                              Comments

                                              There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                              Control0..*
                                              This element is affected by the following invariants: ele-1
                                              TypeExtension
                                              Standard StatusNormative (from Normative)
                                              Alternate Namesextensions, user content
                                              Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                              ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                              SlicingThis element introduces a set of slices on Observation.referenceRange.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                                              • value @ url
                                              • 132. Observation.referenceRange.modifierExtension
                                                Definition

                                                May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

                                                Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

                                                ShortExtensions that cannot be ignored even if unrecognized
                                                Comments

                                                There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                                Control0..*
                                                This element is affected by the following invariants: ele-1
                                                TypeExtension
                                                Is Modifiertrue because Modifier extensions are expected to modify the meaning or interpretation of the element that contains them
                                                Summarytrue
                                                Requirements

                                                Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

                                                Alternate Namesextensions, user content, modifiers
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                                134. Observation.referenceRange.low
                                                Definition

                                                The value of the low bound of the reference range. The low bound of the reference range endpoint is inclusive of the value (e.g. reference range is >=5 - <=9). If the low bound is omitted, it is assumed to be meaningless (e.g. reference range is <=2.3).

                                                ShortLow Range, if relevant
                                                Comments

                                                The context of use may frequently define what kind of quantity this is and therefore what kind of units can be used. The context of use may also restrict the values for the comparator.

                                                Control0..1
                                                This element is affected by the following invariants: ele-1, obs-3
                                                TypeQuantity(SimpleQuantity)
                                                Is Modifierfalse
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                qty-3: If a code for the unit is present, the system SHALL also be present (code.empty() or system.exists())
                                                sqty-1: The comparator is not used on a SimpleQuantity (comparator.empty())
                                                136. Observation.referenceRange.high
                                                Definition

                                                The value of the high bound of the reference range. The high bound of the reference range endpoint is inclusive of the value (e.g. reference range is >=5 - <=9). If the high bound is omitted, it is assumed to be meaningless (e.g. reference range is >= 2.3).

                                                ShortHigh Range, if relevant
                                                Comments

                                                The context of use may frequently define what kind of quantity this is and therefore what kind of units can be used. The context of use may also restrict the values for the comparator.

                                                Control0..1
                                                This element is affected by the following invariants: ele-1, obs-3
                                                TypeQuantity(SimpleQuantity)
                                                Is Modifierfalse
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                qty-3: If a code for the unit is present, the system SHALL also be present (code.empty() or system.exists())
                                                sqty-1: The comparator is not used on a SimpleQuantity (comparator.empty())
                                                138. Observation.referenceRange.type
                                                Definition

                                                Codes to indicate the what part of the targeted reference population it applies to. For example, the normal or therapeutic range.

                                                ShortReference range qualifier
                                                Comments

                                                This SHOULD be populated if there is more than one range. If this element is not present then the normal range is assumed.

                                                Control0..1
                                                This element is affected by the following invariants: ele-1
                                                BindingThe codes SHOULD be taken from ObservationReferenceRangeMeaningCodes
                                                (preferred to http://hl7.org/fhir/ValueSet/referencerange-meaning)

                                                Code for the meaning of a reference range.

                                                TypeCodeableConcept
                                                Requirements

                                                Need to be able to say what kind of reference range this is - normal, recommended, therapeutic, etc., - for proper interpretation.

                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                140. Observation.referenceRange.appliesTo
                                                Definition

                                                Codes to indicate the target population this reference range applies to. For example, a reference range may be based on the normal population or a particular sex or race. Multiple appliesTo are interpreted as an "AND" of the target populations. For example, to represent a target population of African American females, both a code of female and a code for African American would be used.

                                                ShortReference range population
                                                Comments

                                                This SHOULD be populated if there is more than one range. If this element is not present then the normal population is assumed.

                                                Control0..*
                                                This element is affected by the following invariants: ele-1
                                                BindingFor example codes, see ObservationReferenceRangeAppliesToCodes
                                                (example to http://hl7.org/fhir/ValueSet/referencerange-appliesto)

                                                Codes identifying the population the reference range applies to.

                                                TypeCodeableConcept
                                                Requirements

                                                Need to be able to identify the target population for proper interpretation.

                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                142. Observation.referenceRange.age
                                                Definition

                                                The age at which this reference range is applicable. This is a neonatal age (e.g. number of weeks at term) if the meaning says so.

                                                ShortApplicable age range, if relevant
                                                Comments

                                                The stated low and high value are assumed to have arbitrarily high precision when it comes to determining which values are in the range. I.e. 1.99 is not in the range 2 -> 3.

                                                Control0..1
                                                This element is affected by the following invariants: ele-1
                                                TypeRange
                                                Requirements

                                                Some analytes vary greatly over age.

                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                rng-2: If present, low SHALL have a lower value than high (low.empty() or high.empty() or (low <= high))
                                                144. Observation.referenceRange.text
                                                Definition

                                                Text based reference range in an observation which may be used when a quantitative range is not appropriate for an observation. An example would be a reference value of "Negative" or a list or table of "normals".

                                                ShortText based reference range in an observation
                                                Comments

                                                Note that FHIR strings SHALL NOT exceed 1MB in size

                                                Control0..1
                                                This element is affected by the following invariants: ele-1
                                                Typestring
                                                Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                146. Observation.hasMember
                                                Definition

                                                This observation is a group observation (e.g. a battery, a panel of tests, a set of vital sign measurements) that includes the target as a member of the group.

                                                ShortRelated resource that belongs to the Observation group
                                                Comments

                                                When using this element, an observation will typically have either a value or a set of related resources, although both may be present in some cases. For a discussion on the ways Observations can assembled in groups together, see Notes below. Note that a system may calculate results from QuestionnaireResponse into a final score and represent the score as an Observation.

                                                Control0..*
                                                This element is affected by the following invariants: ele-1
                                                TypeReference(Observation, QuestionnaireResponse, MolecularSequence)
                                                Summarytrue
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                                148. Observation.derivedFrom
                                                Definition

                                                The target resource that represents a measurement from which this observation value is derived. For example, a calculated anion gap or a fetal measurement based on an ultrasound image.

                                                ShortRelated measurements the observation is made from
                                                Comments

                                                All the reference choices that are listed in this element can represent clinical observations and other measurements that may be the source for a derived value. The most common reference will be another Observation. For a discussion on the ways Observations can assembled in groups together, see Notes below.

                                                Control0..*
                                                This element is affected by the following invariants: ele-1
                                                TypeReference(DocumentReference, ImagingStudy, Media, QuestionnaireResponse, Observation, MolecularSequence)
                                                Summarytrue
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                ref-1: SHALL have a contained resource if a local reference is provided (reference.startsWith('#').not() or (reference.substring(1).trace('url') in %rootResource.contained.id.trace('ids')))
                                                150. Observation.component
                                                Definition

                                                Some observations have multiple component observations. These component observations are expressed as separate code value pairs that share the same attributes. Examples include systolic and diastolic component observations for blood pressure measurement and multiple component observations for genetics observations.

                                                ShortComponent results
                                                Comments

                                                For a discussion on the ways Observations can be assembled in groups together see Notes below.

                                                Control0..*
                                                This element is affected by the following invariants: ele-1
                                                TypeBackboneElement
                                                Must Supporttrue
                                                Summarytrue
                                                Requirements

                                                Component observations share the same attributes in the Observation resource as the primary observation and are always treated a part of a single observation (they are not separable). However, the reference range for the primary observation value is not inherited by the component values and is required when appropriate for each component observation.

                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                152. Observation.component.id
                                                Definition

                                                Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

                                                ShortUnique id for inter-element referencing
                                                Control0..1
                                                Typestring
                                                XML FormatIn the XML format, this property is represented as an attribute.
                                                154. Observation.component.extension
                                                Definition

                                                May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

                                                ShortAdditional content defined by implementations
                                                Comments

                                                There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                                Control0..*
                                                This element is affected by the following invariants: ele-1
                                                TypeExtension
                                                Standard StatusNormative (from Normative)
                                                Alternate Namesextensions, user content
                                                Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                                SlicingThis element introduces a set of slices on Observation.component.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
                                                • value @ url
                                                • 156. Observation.component.modifierExtension
                                                  Definition

                                                  May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

                                                  Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

                                                  ShortExtensions that cannot be ignored even if unrecognized
                                                  Comments

                                                  There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

                                                  Control0..*
                                                  This element is affected by the following invariants: ele-1
                                                  TypeExtension
                                                  Is Modifiertrue because Modifier extensions are expected to modify the meaning or interpretation of the element that contains them
                                                  Summarytrue
                                                  Requirements

                                                  Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

                                                  Alternate Namesextensions, user content, modifiers
                                                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                  ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
                                                  158. Observation.component.code
                                                  Definition

                                                  Describes what was observed. Sometimes this is called the observation "code".

                                                  ShortType of component observation (code / type)
                                                  Comments

                                                  All code-value and component.code-component.value pairs need to be taken into account to correctly understand the meaning of the observation.

                                                  Control1..1
                                                  This element is affected by the following invariants: ele-1
                                                  BindingThe codes SHOULD be taken from UK Core Observation Type
                                                  (preferred to https://fhir.hl7.org.uk/ValueSet/UKCore-ObservationType)

                                                  A code from the SNOMED Clinical Terminology UK coding system describing a type of observation

                                                  TypeCodeableConcept
                                                  Summarytrue
                                                  Requirements

                                                  Knowing what kind of observation is being made is essential to understanding the observation.

                                                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                  160. Observation.component.value[x]
                                                  Definition

                                                  The information determined as a result of making the observation, if the information has a simple value.

                                                  ShortActual component result
                                                  Comments

                                                  Used when observation has a set of component observations. An observation may have both a value (e.g. an Apgar score) and component observations (the observations from which the Apgar score was derived). If a value is present, the datatype for this element should be determined by Observation.code. A CodeableConcept with just a text would be used instead of a string if the field was usually coded, or if the type associated with the Observation.code defines a coded value. For additional guidance, see the Notes section below.

                                                  Control0..1
                                                  This element is affected by the following invariants: ele-1
                                                  TypeChoice of: Quantity, CodeableConcept, string, boolean, integer, Range, Ratio, SampledData, time, dateTime, Period
                                                  [x] NoteSeeChoice of Data Typesfor further information about how to use [x]
                                                  Primitive ValueThis primitive element may be present, or absent, or replaced by an extension
                                                  Summarytrue
                                                  Requirements

                                                  An observation exists to have a value, though it might not if it is in error, or if it represents a group of observations.

                                                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                  162. Observation.component.dataAbsentReason
                                                  Definition

                                                  Provides a reason why the expected value in the element Observation.component.value[x] is missing.

                                                  ShortWhy the component result is missing
                                                  Comments

                                                  "Null" or exceptional values can be represented two ways in FHIR Observations. One way is to simply include them in the value set and represent the exceptions in the value. For example, measurement values for a serology test could be "detected", "not detected", "inconclusive", or "test not done".

                                                  The alternate way is to use the value element for actual observations and use the explicit dataAbsentReason element to record exceptional values. For example, the dataAbsentReason code "error" could be used when the measurement was not completed. Because of these options, use-case agreements are required to interpret general observations for exceptional values.

                                                  Control0..1
                                                  This element is affected by the following invariants: ele-1, obs-6
                                                  BindingUnless not suitable, these codes SHALL be taken from DataAbsentReason
                                                  (extensible to http://hl7.org/fhir/ValueSet/data-absent-reason)

                                                  Codes specifying why the result (Observation.value[x]) is missing.

                                                  TypeCodeableConcept
                                                  Requirements

                                                  For many results it is necessary to handle exceptional values in measurements.

                                                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                  164. Observation.component.interpretation
                                                  Definition

                                                  A categorical assessment of an observation value. For example, high, low, normal.

                                                  ShortHigh, low, normal, etc.
                                                  Comments

                                                  Historically used for laboratory results (known as 'abnormal flag' ), its use extends to other use cases where coded interpretations are relevant. Often reported as one or more simple compact codes this element is often placed adjacent to the result value in reports and flow sheets to signal the meaning/normalcy status of the result.

                                                  Control0..*
                                                  This element is affected by the following invariants: ele-1
                                                  BindingUnless not suitable, these codes SHALL be taken from ObservationInterpretationCodes
                                                  (extensible to http://hl7.org/fhir/ValueSet/observation-interpretation)

                                                  Codes identifying interpretations of observations.

                                                  TypeCodeableConcept
                                                  Requirements

                                                  For some results, particularly numeric results, an interpretation is necessary to fully understand the significance of a result.

                                                  Alternate NamesAbnormal Flag
                                                  Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
                                                  166. Observation.component.referenceRange
                                                  Definition

                                                  Guidance on how to interpret the value by comparison to a normal or recommended range.

                                                  ShortProvides guide for interpretation of component result
                                                  Comments

                                                  Most observations only have one generic reference range. Systems MAY choose to restrict to only supplying the relevant reference range based on knowledge about the patient (e.g., specific to the patient's age, gender, weight and other factors), but this might not be possible or appropriate. Whenever more than one reference range is supplied, the differences between them SHOULD be provided in the reference range and/or age properties.

                                                  Control0..*
                                                  TypeSeettp://hl7.org/fhir/StructureDefinition/Observation#Observation.referenceRange
                                                  Requirements

                                                  Knowing what values are considered "normal" can help evaluate the significance of a particular result. Need to be able to provide multiple reference ranges for different contexts.