Release 4 5

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Work Group Clinical Decision Support icon Maturity Level : 2 Standards Status : Trial Use

14.2 Definitional Resources

Part of defining knowledge artifacts such as order sets, protocols, and decision support rules is describing in a patient- or context-independent way the activities to be performed. For example, when defining an order set, the orderable items must be described with enough detail to enable the creation of the items when the order set is applied. These descriptions can be thought of as templates for the creation of patient- or context-specific resources and are often referred to as definitional resources, to distinguish them from intent resources (that signal an intention to take some action for a specific patient), as well as event resources (that signal that some action has actually been taken for a patient).

In the most general case, these definitional resources only need to describe the most basic aspects of the activity to be performed, such as:

  • Who - Which person should perform the activity, often specified as a participant role such as a provider specialty.
  • What - What type of activity should be performed, often specified simply as a category or a concept.
  • When - When the activity should be performed, often specified relative to the time the plan is applied.
  • Where - Where the activity should take place, often specified as a facility role.
  • Why - Why the activity should be performed

However, this level of conceptual description often does not carry enough information to enable computable description of activities. For example, medication activities will often involve specific drug and dosage information that must be captured as part of the definition. Further, it is often the case that the values for the elements of resources to be created cannot be specified exactly as part of the definition, but must be specified using a formula that allows for the calculation to be based on patient- or context-specific information.

Note to implementers: Although there are currently very few definitional resources defined (ActivityDefinition, ObservationDefinition, SpecimenDefinition), the concept is general, and this is a deliberate design decision to avoid the overhead of defining and maintaining a different definitional resource for every category of request. We anticipate that as the use cases of ActivityDefinition require more specialized elements to be added, additional definitional resources may be defined.

14.2.1 ActivityDefinition

The ActivityDefinition resource supports the description of definitional resources within FHIR:

Who participantType Specifies the type of participant that should perform the activity.
What kind and code Specifies the type of activity to be performed.
When timing Specifies when the activity should be performed.
Where location Specifies where the activity should be performed.
Why reason, documentation Specifies why the activity should be performed.
14.2.1.1 Referral Request

For example, the following fragment illustrates a definition to create a referral request: 

<ActivityDefinition>
  <description value="refer to primary care mental-health integrated care program for evaluation and treatment
   of mental health conditions now"/>
  <kind value="ServiceRequest"/>
  <code>
    <coding>
      <system value="http://snomed.info/sct"/>
      <code value="306206005"/>
    </coding>
  </code>
  <timingTiming>
    <event>
      <extension url="http://hl7.org/fhir/StructureDefinition/cqf-expression">
        <valueExpression>
          <language value="text/cql"/>
          <expression value="Now()"/>
        </valueExpression>
      </extension>
    </event>
  </timingTiming>
  <participantType value="practitioner"/>
</ActivityDefinition>

Note the use of an expression to represent the value of the timing element as Now() .

14.2.1.2 Medication Request

For medication activities, the ActivityDefinition resource has some basic elements such as the product and quantity , and dosageInstruction but there are cases where elements that need to be set on the resulting MedicationRequest are not present on the ActivityDefinition (such as dispenseRequest ). In those cases, the dynamicValue expression elements can be used to describe the values for elements that are present on the target resource, but not in the definitional resource. For example: 

<ActivityDefinition>
  <id value="citalopramPrescription"/>
  <status value="draft"/>
  <category value="drug"/>
  <productReference>
    <reference value="#citalopramMedication"/>
  </productReference>
  <dynamicValue>
    <path value="dispenseRequest.numberOfRepeatsAllowed"/>
    <expression>
      <language value="text/cql"/>
      <expression value="3"/>
    </expression>
  </dynamicValue>
  <dynamicValue>
    <path value="dispenseRequest.quantity"/>
    <expression>
      <language value="text/cql"/>
      <expression value="30 '{tbl}'"/>
    </expression>
  </dynamicValue>
</ActivityDefinition>
14.2.1.3 Observation

Note The ObservationDefinition resource supports the definition of an observation to implementers: Although there is currently only one definitional be taken.

14.2.1.4 Specimen

The SpecimenDefinition resource defined (ActivityDefinition), supports the concept is general, and this was definition of a deliberate design decision specimen to avoid be collected.

14.2.1.5 Message

The MessageDefinition resource supports the overhead definition of defining and maintaining a different definitional message to be communicated. NOTE: This is a system-level message, as opposed to a human-to-human message, which would be modeled using the CommunicationRequest and Communication resources.

14.2.1.6 Questionnaire

The Questionnaire resource can be used to directly support describing information to be collected as part of a process. The Structured Data Capture icon implementation guide provides detailed information for every category supporting this use case.

14.2.1.7 Event Resources

Note that the ActivityDefinition resource is specifically designed to support request resources, typically with an intent of request. We anticipate proposal to ensure that clinician interaction can be part of interpreting the results of any automated reasoning processes. However, it is possible to construct event resources as part of the reasoning process, such as Observations, Procedures, RiskAssessments, DetectedIssues, etc. To support this case, implementations should make use cases of ActivityDefinition require more specialized elements to a Task resource with proposal intent, where the focus of the Task would be added, the computed event resource.

14.2.1.8 EvidenceVariable

The EvidenceVariable resource may supports the description of definitional resources for variables to be split. referenced from an Evidence resource:

Who topic Could specify the category of evidence variable (eg condition, exposure); available for future uses
What characteristic.definition[x] Specifies a component of the definition of the evidence variable
When characteristic.timeFromStart Subelement of characteristic to specify when the definitional component was or will be determined
Where type Specifies the type of variable (eg dichotomous. Categorical, continuous, descriptive)
How Characteristic.method Specifies how the definitional component was or will be determined

For example, the following fragment illustrates a definition of "intracranial hemorrhage within 7 days" as a characteristic from an EvidenceVariable instance: 

<characteristic>
  <description value="intracranial hemorrhage within 7 days"/>
  <definitionCodeableConcept>
    <coding>
      <system value="http://snomed.info/sct"/>
      <code value="1386000"/>
      <display value="Intracranial hemorrhage (disorder)"/>
    </coding>
  </definitionCodeableConcept>
  <timeFromStart>
    <description value="within 7 days"/>
    <range>
      <low>
        <value value="0"/>
        <unit value="day"/>
        <system value="http://unitsofmeasure.org"/>
        <code value="d"/>
      </low>
      <high>
        <value value="7"/>
        <unit value="day"/>
        <system value="http://unitsofmeasure.org"/>
        <code value="d"/>
      </high>
    </range>
  </timeFromStart>
</characteristic>