Evidence Based Medicine on FHIR Implementation Guide
1.0.0-ballot - ballot
Evidence Based Medicine on FHIR Implementation Guide
1.0.0-ballot - ballot
Evidence Based Medicine on FHIR Implementation Guide, published by HL7 International / Clinical Decision Support. This guide is not an authorized publication; it is the continuous build for version 1.0.0-ballot built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/ebm/ and changes regularly. See the Directory of published versions
The Group Resource represents a defined collection of entities. The group may be enumerated, meaning that there is a known quantity of group members with or without a listing of the group members. The group may be definitional, meaning there is a structured representation of the characteristics (criteria) that define membership eligiblity, or who or what matches the criteria to be considered a member of the group.
The Group.type element is used to classify the type of group member in terms of FHIR types with options limited to person, animal, practitioner, device, careteam, healthcareservice, location, organization, relatedperson, and specimen. Group.type is a required element in the use of Group Resource for health data exchange.
In other words, type is letting you know the type of group (Person, Specimen,…). The choices in Group.type are limited to concepts represented in FHIR. If type is person, then the members would have to be resources of type person. If type is device, you will expect a different set of resources.
In FHIR version R5, the Group.type element is required. In FHIR version R6, the Group.type element is required if the Group.membership element has a value of definitional or enumerated.
The Group.membership element is used to classify the Group Resource as either definitional or enumerated, and is a required element.
enumerated: Use this code if you desire to list the group members and/or specify the number of entities in the group.
definitional: Use this code if the Group.characteristic value(s) specified are both necessary and sufficient to determine qualifications for membership (for defining what makes something a member of the group). If a group is both enumerated and definitional, then use the enumerated code.
In FHIR version R6, a third code (conceptual) is allowed for the Group.membership element value, and Group.type is not required when Group.membership = ‘conceptual’. This allows greater flexibility as needed for science data exchange.
In the EBMonFHIR Implementation Guide, which is built on FHIR version R5 so must respect the Group.type and Group.membership requirements, there is no constraints or extensions to change the type or membership element values to concepts not fitting the base requirements. When a Group would be considered ‘conceptual’ the examples will use ‘definitional’ and when a Group would not use the type element the example will use ‘animal’ (as the least likely value to be confused for a real value in the examples used in the EBMonFHIR Implementation Guide).
Group.code is used to describe the kind of group members, especially when a more specific classification than the Group.type value is desired. For example, if Group.type is ‘animal’, then Group.code may be ‘cow’. If Group.type is ‘device’, then Group.code could be ‘syringe’ or ‘cytometer’.
Group.quantity is a count of group members, so it must be an integer if used.
The base Group Resource in FHIR version R5 uses a repeatable characteristic element to define inclusion and exclusion criteria. This characteristic element includes 4 elements:
.. code which is a required CodeableConcept to represent the type of characterstic.
.. value[x] with is a required element, with datatype of CodeableConcept, boolean, Quantity, Range, or Reference, to represent the matching value for the type of characteristic
.. exclude which is a required boolean to determine if this is an inclusion or exclusion criterion
.. period which is an optional Period for when in calendar time the characteristic applies
Each characteristic must have a code value (CodeableConcept datatype) to specify the attribute.
For a characteristic of “age > 18 years” the attribute is “age” and the attribute of age may be expressed as:
“code”: { “coding”: [ { “system”: “http://snomed.info/sct”, “code”: “397669002”, “display”: “Age” } ] }
For a characteristic of “Body mass index >= 30 kg/m2” the attribute is “Body mass index” and the attribute may be expressed as:
"code": {
"coding": [
{
"system": "http://loinc.org",
"code": "39156-5",
"display": "Body mass index (BMI) [Ratio]"
}
]
}
(Examples taken from https://fevir.net/resources/Group/171819)
Each characteristic must have a value[x] value to specify the value of the attribute that holds for members of the group. There is no [x] in the JSON or XML expression as it is replaced with the data type (CodeableConcept, boolean, Quantity, Range, Reference, or in FHIR version R6 uri or Expression)
For a characteristic of “age > 18 years” the value is “> 18 years” and the value may be expressed with a Quantity datatype as:
“valueQuantity”: { “comparator”: “>=”, “value”: 18, “unit”: “years”, “system”: “http://unitsofmeasure.org”, “code”: “a” }
Ror a characteristic of “Body mass index >= 30 kg/m2” the value is “>= 30 kg/m2” and the value may be expressed as:
“valueQuantity”: { “comparator”: “>=”, “value”: 30, “unit”: “kg/m2”, “system”: “http://unitsofmeasure.org”, “code”: “kg/m2” }
(Examples taken from https://fevir.net/resources/Group/171819)
Sometimes group membership is determined by characteristics not possessed. When this is the case, the Group.characteristic.exclude element has a value of true (“exclude”: true). For characteristics that are not exclusion criteria, the Group.characteristic.exclude element has a value of false (“exclude”: false). The exclude element is required.
For example, an exclusion criterion of HbA1c ≥ 14.0% is expressed as:
{ “code”: { “coding”: [ { “system”: “http://loinc.org”, “code”: “59261-8”, “display”: “Hemoglobin A1c/Hemoglobin.total in Blood” } ] }, “valueQuantity”: { “value”: 14, “comparator”: “>=”, “unit”: “%”, “system”: “http://unitsofmeasure.org”, “code”: “%” }, “exclude”: true }
modified off:
StudyEligibilityCriteria: Eligibility Criteria for Bariatric Surgery Randomized Trial (Diabetes Surgery Study) [Database Entry: FHIR Group Resource]. Contributors: Brian S. Alper [Authors/Creators]. In: Fast Evidence Interoperability Resources (FEvIR) Platform, FOI 170443. Revised 2022-09-09. Available at: https://fevir.net/resources/Group/170443. Computable resource at: https://fevir.net/resources/Group/170443.
The Group.member element is a BackboneElement (multiple elements per instance) and may have any number of instances. Each instance refers to an actual member of the group. Each member must be represented in an entity element (Group.member.entity) which uses a Reference datatype, and each member may optionally have a period element (Group.member.period) with a Period datatype for the timeframe of group membership and an inactive element (Group.member.inactive) with a boolean datatype to denote if a member is no longer in the group.
The GroupR6 Profile is a base for all other Group Profiles. Extensions for metadata about the Group Resource include url, version, versionAlgorithmString, title, experimental, date, publisher, contact, useContext, purpose, copyright, copyrightLabel, author, and relatedArtifact. A modifierExtension for status allows specifying whether the Resource is active, draft, or retired. An extension for characteristicExpression allows use of an Expression datatype to represent the group definition instead of using the characteristic element.
Extensions for combinationMethod (valueCode choices of all-of, any-of, at-least, at-most, except-subset) and combinationThreshold (valuePositiveInt for use with at-least or at-most) express how 2 or more characteristic instances are combined.
The Group.combinationMethod extension is used when there are two or more Group.characteristic instances to define how the characteristics are combined.
The Group.combinationThreshold extension provides the value of “n” when at-least or at-most codes are used for the Group.combinationMethod extension (see above)
The characteristic element has multiple extensions to support more ways of defining eligibility criteria.
.. valueUri and valueExpression provide additional datatypes for the value of the characteristic
.. description uses a markdown datatype and supports a human-readable description of the characteristic. A short, natural language description of the characteristic could be used to communicate the criterion to an end-user. The description element is for convenience so that end users can understand the characteristic and is neither a required part of the characteristic nor part of the structured representation of the characteristic.
.. method uses a CodeableConcept datatype and supports specification of how the value of the characteristic is determined. The method modifies the Group.characteristic.code and indicates how the value is to be determined. For example, HbA1c values can be determined by High-Performance Liquid Chromatography (HPLC) or by capillary electrophoresis. The method may be expressed as multiple concepts, e.g. standing barefoot for height measurements could be expressed as two separate concepts (standing and barefoot) that express the method.
.. determinedByReference uses a Reference datatype to specify a Device, DeviceMetric, or DeviceDefinition used to determine the value of the characteristic
.. determinedByExpression uses an Expression datatype to specify the formula or calculation used to determine the value of the characteristic
In the FHIR version R6 Group Resource, Group.characteristic.determinedBy[x] modifies the Group.characteristic.code and indicates how the value is to be determined, using either a Reference datatype or an Expression datatype. This provides a means of expressing or modifying the method, not as a set of concepts, but as either a reference to a device or as an Expression. The reference to a device can be either to a specific device using the Device Resource or the DeviceMetric Resource if a specific set of device parameters is needed, or a type of device using the DeviceDefinition Resource.
.. offset uses a CodeableConcept datatype and supports specification of a reference point from which the value is measured, e.g., 2 units above the upper normal limit would be expressed with a valueQuantity of 2 units and an offset with a coding for Upper Normal Limit. The offset defines the reference point for comparison when other than 0. To express a characteristic of a calcium level greater than the normal limit or a hemoglobin level less than 1 g/dL below the reference range, the offset concept would represent “normal limit” or “reference range”. This is a modifier element because it modifies the meaning of the characteristic.value[x].
.. instancesQuantity and instancesRange are used to express the number of times the characteristic is met, i.e. the number of occurrences meeting the characteristic. There should be a constraint on the Quantity.value and Range.low.value and Range.high.value that it can only be non-negative whole numbers.
.. durationDuration and durationRange are used to express how long the characteristic is met, i.e. the length of time in which the characteristic is met.
.. timing uses a complex expression (matching the RelativeTime datatype in FHIR version R6) to express timing relative to an event or context other than calendar time, e.g. within a month following patient discharge.
Note: RelativeTime is a new datatype in FHIR version R6. RelativeTime is used to express a point in time or an interval of time relative to an event defined in data types other than dateTime.
Example representing “at 12 months form inclusion in a clinical trial” from https://fevir.net/resources/Group/172484 with inclusion defined as enrollment:
“timing”: [ { “contextCode”: { “coding”: [ { “system”: “http://snomed.info/sct”, “code”: “709491003”, “display”: “Enrollment in clinical trial” } ] }, “offsetDuration”: { “value”: 12, “unit”: “months”, “system”: “http://unitsofmeasure.org”, “code”: “mo” }, “text”: “at 12 months” }
The CohortDefinition Profile is a Profile of GroupR6 that is used to provide a conceptual or definitional representation of a group. In FHIR version R6, membership = conceptual allows avoiding the required use of type. In this IG for FHIR version R5, membership is definitional and the type value can be ignored for resource content processing. The quantity and member elements are not used in the CohortDefinition Profile. The CohortDefinition Profile is used to support characteristics that are combinations of two or more characteristics.
For example, a group defined by females who are are > 20 years old or have red hair would be defined with combinationMethod = ‘all-of’ and 2 characteristic instances: {code sex, valueCodeableConcept female} and {code Defined by Reference, valueReference CohortDefinition: > 20y or red hair}. The CohortDefinition: > 20y or red hair would be defined with combinationMethod = ‘any-of’ and 2 characteristic instances: {code age, valueQuantity > 20 years} and {code hair color, valueCodeableConcept red}.
Profiles of CohortDefinition used for the inclusion and exclusion criteria of specific conceptual types of groups include the StudyEligibilityCriteria Profile (for a research study), the RecommendationEligibilityCriteria Profile (for a clinical practice guideline recommendation), the SystematicReviewEligibilityCriteria Profile (for a systematic review), the MetaanalysisEligibilityCriteria Profile (for a statistical meta-analysis), and the SearchStrategy Profile (for a literature search). These Profiles are not currently structurally different than CohortDefinition but are separated for future development in case of specialized developments for eligibility criteria.
The ExposureDefinition, ComparatorDefinition, OutcomeDefinition, and MetaanalysisOutcomeDefinition Profiles are Profiles of CohortDefinition used for the definition of evidence variables. These Profiles are not currently structurally different than CohortDefinition but are separated for future development in case of specialized developments for variable definitions.
The ExposureGroup and ComparatorGroup Profiles are Profiles of GroupR6 used to support ‘enumerated’ groups. When the evidence is about groups that can be typed to FHIR types, the type element can be used and the membership element can be set to ‘enumerated’ In FHIR version R6, when the evidence is not about groups that can be typed to FHIR types, the membership element can be set to ‘conceptual’ to signal non-use of the type element. These Profiles are provided for future development and to maintain consistency between R5 and R6 versions.
The NetEffectContributions Profile is a Profile of GroupR6 used to represent an enumerated group of participants in a net effect analysis where the participants are Evidence Resources (NetEffectContribution Profile). Because Evidence Resources are not among the allowed values in Group.type and not among the allowed values in Group.member.entity, the type of group member is expressed as “Net Effect Contribution” in Group.code.text and the method of listing group members is to use a single characteristic with a code.text value of “Member of” and a valueReference which references a NetEffectContributionList Profile of List Resource.
The StudyGroup Profile is a Profile of GroupR6 used to represent an enumerated group of participants in a research study. The membership value is set to ‘enumerated’.
The MetaanalysisStudyGroup Profile is a Profile of GroupR6 used to represent an enumerated group of participants in a meta-analysis where the participants are Evidence Resources. Because Evidence Resources are not among the allowed values in Group.type and not among the allowed values in Group.member.entity, the type of group member is expressed as “Evidence” in Group.code.text and the method of listing group members is to use a single characteristic with a code.text value of “Member of” and a valueReference which references an EvidenceList Profile of List Resource.
The EvidenceReportSubject Profile is a Profile of CohortDefinition used to define the subject of an EvidenceReport. The report subject is defined conceptually as a combination (‘all-of’) of characteristics. Any characteristic is optional (as there are many types of evidence reports) but common types of characteristics suggested in the Implementation Guide include Population (referencing Group), Intervention or Exposure (referencing EvidenceVariable or Group), Comparator (referencing EvidenceVariable or Group), and Outcomes (referencing OutcomeList).
The ComparativeEvidenceReportSubject Profile is a Profile of EvidenceReportSubject which requires the use of Population (constrained to reference StudyGroup), Intervention or Exposure (constrained to reference VariableDefinition or ExposureDefinition), Comparator (constrained to reference VariableDefinition or ExposureDefinition or ComparatorDefinition), and Outcomes (constrained to reference OutcomeList).
IG © 2022+ HL7 International / Clinical Decision Support. Package hl7.fhir.uv.ebm#1.0.0-ballot based on FHIR 5.0.0. Generated 2024-04-27
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