US Core Implementation Guide
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This page is part of the US Core (v7.0.0-ballot: STU7 Ballot 1) based on FHIR (HL7® FHIR® Standard) R4. The current version which supersedes this version is 6.1.0. For a full list of available versions, see the Directory of published versions

Must Support

Page standards status: Informative

The Profile elements consist of Mandatory, Must Support, and Additional USCDI Requirements elements. The sections below defines the server and client expectations for processing these elements and illustrates how they are displayed and documented.

Mandatory Elements

Mandatory elements are elements with a minimum cardinality of 1 (min=1). When an element is Mandatory, the data is expected to always be present. Very rarely, it may not be, and guidance for when data is missing is provided in the Missing Data section and the next section. The convention in this guide is to mark all min=1 elements as Must Support unless they are nested under an optional element. An example of this is CarePlan.status.

Must Support Elements

For querying and reading US Core Profiles, Must Support on any profile data element SHALL be interpreted as follows (see the Future of US Core page for writing and updating US Core Profiles):

  • US Core Responders SHALL be capable of populating all data elements as part of the query results as specified by the US Core Server Capability Statement.
  • US Core Requestors SHALL be capable of processing resource instances containing the data elements without generating an error or causing the application to fail. In other words, US Core Requestors SHOULD be capable of displaying the data elements for human use or storing it for other purposes.
  • In situations where information on a particular data element is not present, and the reason for absence is unknown, US Core Responders SHALL NOT include the data elements in the resource instance returned as part of the query results.
  • When querying US Core Responders, US Core Requestors SHALL interpret missing data elements within resource instances as data not present in the US Core Responder’s system.
  • In situations where information on a particular data element is missing or suppressed, refer to the guidance for Missing Data and Suppressed Data. In cases where information on a specific data element is missing and the US Core Responder knows the precise reason for the absence of data (other than suppressed data), US Core Responders SHOULD send the reason for the missing information. This is done by following the same methodology outlined in the Missing Data section but using the appropriate reason code instead of unknown.
  • US Core Requestors SHALL be able to process resource instances containing data elements asserting missing information.

The terms US Core Responder Actor US Core Requestor Actor are used throughout the guide and typically refer to a server or a client.

Readers are advised to understand FHIR Terminology requirements, FHIR RESTful API based on the HTTP protocol, along with FHIR Data Types, FHIR Search, and FHIR Resource formats before implementing US Core requirements.

All the profile information for the US Core Implementation Guide is represented in a single CSV or Excel file. This may be useful to testers and analysts to review the Must Support and Mandatory elements across profiles in a single table.

This Observation Summary Table compares Must Support Elements across all the US Core Observation Profiles.

Additional USCDI Requirements

The US Core Profiles include requirements from the U.S. Core Data for Interoperability (USCDI) v4. Some US Core Profile elements that are needed to represent USCDI Data Elements for ONC Health IT Certification (g(10) certification) are not Mandatory or Must Support because many non-certifying implementers do not need them for their use cases. US Core designates these elements Additional USCDI Requirements.

Implementers seeking ONC certification SHALL interpret Additional USCDI Requirements as Must Support elements as documented above; otherwise, they are considered optional. All Mandatory, Must Support, or Additional USCDI Requirements are in scope for ONC Health IT Certification. See the USCDI page for more information about the US Core and USCDI relationship and a mapping between US Core Profiles and the USCDI Data Classes and Elements.

The table below lists the Additional USCDI Requirements and their corresponding Profiles and FHIR elements.

Additional USCDI Requirements Profile FHIR Element
Contact Detail US Core Patient Profile Patient.telecom
A Communication Language US Core Patient Profile Patient.communication
A Race US Core Patient Profile Patient.extension:race
An Ethnicity US Core Patient Profile Patient.extension:ethnicity
A Tribal Affiliation US Core Patient Profile Patient.extension:tribalAffiliation
A Sex US Core Patient Profile Patient.extension:sex
Gender Identity US Core Patient Profile Patient.extension:genderIdentity
Date Of Death US Core Patient Profile Patient.deceased[x]
Previous Address US Core Patient Profile Patient.address.use or Patient.address.period
Previous Name US Core Patient Profile Patient.name.use or Patient.name.period
Suffix US Core Patient Profile Patient.name.suffix
A Reason Or Indication For Referral Or Consultation US Core ServiceRequest Profile ServiceRequest.reasonCode
A Reason Or Indication For Referral Or Consultation US Core ServiceRequest Profile ServiceRequest.reasonReference
A Reason Or Indication For Referral Or Consultation US Core Procedure Profile Procedure.reasonCode
A Reason Or Indication For Referral Or Consultation US Core Procedure Profile Procedure.reasonReference
The Reason Or Indication For The Prescription US Core MedicationRequest Profile MedicationRequest.reasonCode
The Reason Or Indication For The Prescription US Core MedicationRequest Profile MedicationRequest.reasonReference
Medication Adherence US Core MedicationRequest Profile MedicationRequest.extension:medicationAdherence
A Reference To The Request For The Procedure US Core Procedure Profile Procedure.basedOn
US Core Document Category US Core DocumentReference Profile DocumentReference.category:uscore
References To An Associated Survey, Assessment, Or Screening Tool US Core Simple Observation Profile Observation.derivedFrom
Specimen Source Site US Core Specimen Profile Specimen.collection
Specimen Source Site US Core Specimen Profile Specimen.collection.bodySite
Specimen Condition Acceptability US Core Specimen Profile Specimen.condition

Communicating Additional USCDI Requirements

To communicate when Additional USCDI Requirements elements are in a US Core profile:

  1. The profiles page includes an “Additional USCDI Requirements” listing the elements under the “Mandatory and Must Support Data Elements” section.
  2. The computable US Core USCDI Requirement Extension is added to each element in the profile’s [StructureDefinition].
  3. The formal views of profile content display “ADDITIONAL USCDI:” in the element’s short description (see below for examples).

Presentation of Must Support, Mandatory, and USCDI Requirement Elements in the Formal Profile Views

On each profile page, several different formal views of the US Core Profile contents are displayed in a tree format under tabs labeled “Differential Table”, “Snapshot Table”, and “Key Elements Table”.

Differential Table View

Elements with a cardinality starting with “1” under the column header, “Card.” (e.g., 1..1) are Mandatory elements. Elements labeled Must Support in the “Differential Table” view are flagged with an S. Elements with the label “ADDITIONAL USCDI:” under the header “Description and Constraints” are Additional USCDI Requirements. Figure 1 illustrates an example of this:

Figure 1: Differential Table View
Must_Support_Differential_View.png

Key Elements Table View

The “Key Elements Table” view consists of:

  1. all the Mandatory, Must Support, and Additional USCDI Requirements elements in the differential view
  2. any Mandatory, Must Support, and Additional USCDI Requirements elements inherited from a US Core Profile or other profile from which it is derived. (e.g., US Core Body Height Profile is based on the US Core Vital Signs Profile or US Core QuestionnaireResponse Profile is based on the Structured Data Capture (SDC) Questionnaire Response Profile)
  3. any Mandatory or modifier elements not in 1. or 2.

This view includes the same flags and labels described in Differential Table View:

Figure 2: Snapshot Table (Must Support) View
Must_Support_Key_View.png

Snapshot Table View

The “Snapshot Table” view in Figure 3 view consists of:

  1. all the Mandatory, Must Support, and Additional USCDI Requirements elements in the differential view
  2. any inherited Mandatory, Must Support, and Additional USCDI Requirements elements from a US Core or other profile upon which it is based. (e.g., US Core Body Height Profile based on Vital Signs Profile or US Core QuestionnaireResponse Profile based on Structured Data Capture (SDC) Questionnaire Response Profile)
  3. any base FHIR elements not in 1. or 2.

This view includes the same flags and labels as described in Differential Table View:

Figure 3: Snapshot Table View
Must_Support_Snapshot_View.png

Defined Pattern Elements

The StructureDefinitions define the US Core Profiles and the ElementDefinition.pattern, which is used almost exclusively for the CodeableConcept and Coding datatypes. If the element is marked as Must Support and defined by a pattern, then the pattern defines the elements and element values that the server SHALL be capable of providing.

For example, the US Core DiagnosticReport Profile for Laboratory Results Reporting category element is defined with a pattern requiring fixed values in DiagnosticReport.category.coding.system and DiagnosticReport.category.coding.code for a Coding element. When claiming conformance to this profile:

  • US Core Responders SHALL provide these values in a DiagnosticReport.category
  • US Core Requestors SHALL be capable of processing these values in DiagnosticReport.category
Figure 4: US Core DiagnosticReport.category
Must_Support_DiagnosticReport_category.png

Must Support - Primitive Element

Primitive elements are single elements with a primitive value. If they are marked as Must Support, then the server SHALL be capable of providing the element value to meet the Must Support requirement.

For example, the US Core DiagnosticReport Profile for Laboratory Results Reporting issued element is a primitive instant datatype. Therefore, when claiming conformance to this profile:

  • US Core Responders SHALL be capable of providing a value in a DiagnosticReport.issued
  • US Core Requestors SHALL be capable of processing the value in DiagnosticReport.issued
Figure 5: US Core DiagnosticReport.issued
Must_Support_DiagnosticReport_issued.png

Must Support - Complex Elements

Complex elements are composed of primitive and/or other complex elements. Note that coded elements (CodeableConcept, Coding, and code datatypes) also have additional binding rules, which are documented in the Coded Elements section.

For any complex element marked as Must Support, the server SHALL be capable of providing at least one of the sub-element values. If any sub-element is marked as Must Support, it must meet the Must Support requirements as well and satisfy the Must Support requirement for the parent element.

For example, the US Core DiagnosticReport Profile for Report and Note exchange presentedForm element is labeled Must Support and has no Must Support sub-elements. When claiming conformance to this profile:

  • US Core Responders SHALL be capable of providing a value in DiagnosticReport.presentedForm sub-element.
  • US Core Requestors SHALL be capable of processing the value in DiagnosticReport.presentedForm.
Figure 5: US Core DiagnosticReport.presentedForm
Must_Support_DiagnosticReport_presentedForm.png

For example, the US Core Patient Profile name element is labeled Must Support and has Must Support sub-elements “family” and “given”. When claiming conformance to this profile:

  • US Core Responders SHALL be capable of providing a value in Patient.name.family and Patient.name.given.
  • US Core Requestors SHALL be capable of processing the value in value in Patient.name.family and Patient.name.given.
Figure 6: US Core Patient.name
Must_Support_Patient_name.png

On the other hand, if any sub-element is marked as Must Support and the parent element is not, there is no expectation that you must support the parent. However, if the parent element is represented in the structure, you must support the sub-element (s) marked as Must Support. There are no examples of US Core profiles that have this structure defined.

Systems can support the other elements, but this is not a requirement of US Core. The U.S. Core Data for Interoperability (USCDI) may require additional elements, for example, suffix.

Must Support - Resource References

This section documents additional Must Support requirements for the Reference element.

In certain profiles, only specific resource references are labeled as Must Support.

For example, the US Core DocumentReference Profile author US Core Practitioner Profile is labeled Must Support. When claiming conformance to this profile:

  • US Core Responders SHALL be capable of providing a DocumentReference.author with a valid reference to a US Core Practitioner Profile.
  • US Core Requestors SHALL be capable of processing a DocumentReference.author with a valid reference to a US Core Practitioner Profile.

Systems can support other references, but this is not a requirement of US Core.

Figure 7: US Core DocumentReference.author
Must_Support_DocumentReference.png

In specific profiles, only a single resource reference is present on an element labeled Must Support.

For example, the US Core AllergyIntolerance Profile patient is labeled Must Support. When claiming conformance to this profile:

  • US Core Responders SHALL be capable of providing an AllergyIntolerance.patient with a valid reference to a US Core Patient Profile.
  • US Core Requestors SHALL be capable of processing an AllergyIntolerance.patient with a valid reference to a US Core Patient Profile.
Figure 8: US Core AllergyIntolerance.patient
Must_Support_AllergyIntolerance.png

Must Support - Choice of Data Types

Some elements allow different data types (e.g., Observation.effective[x]) for their content. Only specific data type choice elements are labeled as Must Support in these situations.

For example, the US Core Observation Clinical Result Profile effectiveDateTime is labeled Must Support. When claiming conformance to this profile:

  • US Core Responders SHALL be capable of populating Observation.effectiveDateTime.
  • US Core Requestors SHALL be capable of processing Observation.effectiveDateTime.

Systems MAY support populating and processing other choice elements (such as Observation.effectivePeriod), but this is not a requirement of US Core.

Figure 9: US Core Observation.effectiveDateTime
Must_Support_Observation.effective.png

For the US Core Observation Clinical Result Profile value element, multiple elements are labeled Must Support. When claiming conformance to this profile:

  • US Core Responders SHALL be capable of populating Observation.valueQuantity, Observation.valueCodeableConcept, and Observation.valueString.
  • US Core Requestors SHALL be capable of processing Observation.valueQuantity, Observation.valueCodeableConcept, and Observation.valueString.

Systems can support the other elements, but this is not a requirement of US Core.

Figure 10: US Core `Observation.value[x]`
Must_Support_Observation.value.png

Must Support - Choice of Profile Elements

There are several instances in this Guide where there is a choice of supporting one or another profile element to meet the Must Support requirement. In such cases, the server SHALL support at least one element, and the client application SHALL support all elements. Unfortunately, there is no way to define this in a computable way, but these instances are clearly documented in the Profile specific implementation guidance sections.

For example:

US Core MedicationRequest Profile - The MedicationRequest resource can represent that information is from a secondary source using either a boolean flag or reference in MedicationRequest.reportedBoolean, or a reference using MedicationRequest.reportedReference to Practitioner or another resource type. Although both are marked as Must Support, servers are not required to support a boolean and a reference but SHALL choose to support at least one of these elements.