US Core Implementation Guide, published by HL7 International / Cross-Group Projects. This guide is not an authorized publication; it is the continuous build for version 8.0.0-ballot built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/US-Core/ and changes regularly. See the Directory of published versions

Must Support

Page standards status: Trial-use

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

Mandatory Elements

Mandatory elements have a minimum cardinality of 1 (min=1). When an element is Mandatory, the data is expected always to be present. However, very rarely it may be missing, and the Missing Data section and the next section provide guidance when the data is missing. 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 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. This processing may result in a determination not to use the resource if the resource content does not meet business requirements.
• When 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.
• When 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 and 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, FHIR Data Types, FHIR Search, and FHIR Resource formats before implementing US Core requirements.

Additional USCDI Requirements

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

Additional USCDI Requirements	Profile	FHIR Element
A Communication Language	US Core Patient Profile	Patient.communication
An Interpreter Required Flag	US Core Patient Profile	Patient.extension:interpreterRequired
An Interpreter Required Flag	US Core Encounter Profile	Encounter.extension:interpreterRequired
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
Sex Parameter For Clinical Use	US Core Patient Profile	Patient.extension:sexParameterForClinicalUse
Gender Identity	US Core Patient Profile	Patient.extension:genderIdentity
Personal Pronouns	US Core Patient Profile	Patient.extension:personalPronouns
Date Of Death	US Core Patient Profile	Patient.deceased[x]
Address Use	US Core Patient Profile	Patient.address.use
Address Period	US Core Patient Profile	Patient.address.period
Name Use	US Core Patient Profile	Patient.name.use
Name Period	US Core Patient Profile	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.performer
A Reason Or Indication For Referral Or Consultation	US Core Procedure Profile	Procedure.performer.actor
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
Health Status Assessments	US Core Simple Observation Profile	Observation.category:us-core

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 view of the profile content displays "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". Several examples below illustrate the presentation of Must Support elements and their rules. Except where noted, the same rules apply for the Additional USCDI Requirements for certifying systems.

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:

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., the US Core Body Height Profile is based on the US Core Vital Signs Profile, and the 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:

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:

Defined Pattern Elements

The StructureDefinitions define the US Core Profiles and the ElementDefinition.pattern, used almost exclusively for the CodeableConcept and Coding datatypes. If an 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. If an element is marked as Additional USCDI and defined by a pattern, then the pattern defines the elements and element values that the certifying 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

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. If they are marked as Additional USCDI, then the certifying system SHALL be capable of providing the element value to meet the Additional USCDI 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

Must Support - Complex Elements

Complex elements are composed of primitive and other complex elements. Note that coded elements (CodeableConcept, Coding, and code datatypes) also have additional binding rules 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 also meet the Must Support requirements and satisfy the Must Support requirements 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.

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 Patient.name.family and Patient.name.given.

On the other hand, if any sub-element is marked as Must Support or Additional USCDI 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, servers SHALL support the sub-element(s) marked as Must Support and certifying system SHALL the sub-elements labeled as Additional USCDI.

For example, the US Core Patient Profile telecom element is not labeled Must Support, but telecom.system, telecom.value, telecom.use are. When claiming conformance to this profile:

• If US Core Responders support Patient.telecom, they SHALL be capable of providing values in Patient.telecom.system , Patient.telecom.value, and Patient.telecom.use.
• US Core Requestors SHALL be capable of processing the values in Patient.telecom.

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 such as Patient.suffix.

Must Support - Resource References

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

Must Support - Choice of Data Types

If a Must Support element has a choice of datatypes for its content, the datatypes the server SHALL support are labeled as Must Support. If an Additional USCDI element has a choice of datatypes for its content, the datatypes the certifying system SHALL support are labeled as Must Support.

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.

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.

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 or Additional USCDI requirements. In such cases, the server or certifying system 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 documented in the Profile specific implementation guidance sections.

For example: