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

Observations are a key aspect of healthcare. This resource is used to capture those that do not require more sophisticated mechanisms.

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.

A unique identifier assigned to this observation.

Allows observations to be distinguished and referenced.

The reference to a FHIR ObservationDefinition resource that provides the definition that is adhered to in whole or in part by this Observation instance.

ObservationDefinition can be referenced by its canonical url using instantiatesCanonical, or by a name or an identifier using the appropriate sub-elements of instantiatesReference.

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.

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

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

Reference to the triggering observation.

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

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

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

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

The status of the result value.

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

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

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

Used for filtering what observations are retrieved and displayed.

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.

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

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

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.

The patient, or group of patients, location, device, organization, procedure or practitioner this observation is about and into whose or what 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.

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

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. The subject of an Observation may in some cases be a procedure. This supports the regulatory inspection use case where observations are captured during inspections of a procedure that is being performed (independent of any particular patient or whether patient related at all).

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. As another use case, a caregiver (RelatedPerson) has back strain and is unable to provide ADL support to a patient (Subject).

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 http://hl7.org/fhir/StructureDefinition/observation-focusCode.

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

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

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).

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.

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

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.

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

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.

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

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

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

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

• An observation may have:
  1. a single value here
  2. both a value and a set of related or component values
  3. only a set of related or component values.
• If a value is present, the datatype for this element should be determined by the code.
• 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 code defines a coded value.
• Attachment is used if the observation result value is a binary file such as an image. If the observation result value is derived from the binary file (for example 'X' detected and here is the the proof in this image), the binary file may be directly represented using DocumentReference and referenced by derivedFrom.
• The usage of valueReference is restricted to the MolecularSequence resource when used as a definitional resource, not as a patient-specific finding. .
• For additional guidance, see the Notes section below.

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

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

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.

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

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

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.

Comments about the observation or the results.

Need to be able to provide free text additional information.

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.

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

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.

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

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

Indicates the mechanism used to perform the observation.

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

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

The specimen that was used when this observation was made.

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).

A reference to the device that generates the measurements or the device settings for the device.

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.

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.

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.

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.

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).

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).

The value of the normal value of the reference range.

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

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

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

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.

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

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

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.

Some analytes vary greatly over age.

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".

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.

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.

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.

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.

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.

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, reference range, dataAbsentReason, and interpretation can differ between the components and are not inherited; these should be provided if appropriate.

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

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

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

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

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

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

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 the code.
• 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 code defines a coded value.
• Attachment is used if the observation result value is a binary file such as an image. If the observation result value is derived from the binary file (for example 'X' detected and here is the the proof in this image), the binary file may be directly represented using DocumentReference and referenced by derivedFrom.
• If a value is present, the datatype for this element should be determined by the code.
• 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 code defines a coded value.
• Attachment is used if the observation result value is a binary file such as an image. If the observation result value is derived from the binary file (for example 'X' detected and here is the the proof in this image), the binary file may be directly represented using DocumentReference and referenced by derivedFrom.
• The usage of valueReference is restricted to the MolecularSequence resource when used as a definitional resource, not as a patient-specific finding. .
• For additional guidance, see the Notes section below.

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

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

"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.

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

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

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.

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

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.

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.