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

Writing Vital Signs

Examples

Patient-facing

• A provider creates an order in an EHR for patient home monitoring. Then, the patient's blood pressure cuff sends data to an app on their phone that writes it into their record. The EHR automatically associates the blood pressure data with the appropriate order.
• A patient uses an app to retrieve their vital signs from the EHR, which were recorded during a specialist visit, and they write them to the EHR used by their primary care provider. The provider can review the vital signs within the EHR and incorporate them into the record.

Provider-facing

• A blood pressure cuff sends readings to an app on a practice tablet that a clinical user uses to write the data to a patient's record in the EHR.
• A patient app saves data to a repository controlled by the app developer. Then, the patient uses a "share with provider" function to enable the provider to access this data with an app installed in the provider's EHR. The provider writes some or all of the observations into the patient's record in the EHR.

Configuration

Servers SHALL document support for writing Observation resources in their Capability Statements by including a CapabilityStatement.rest.resource[type=Observation].interaction with a code of create. Servers that support the ability to update Observation resources SHALL also include an interaction with a code of update.

SMART Scopes

Patient-facing apps

Servers providing the ability to write FHIR vital sign Observation resources from patient-facing apps SHALL support the registration and authorization of apps with the patient/Observation.c?category=http://terminology.hl7.org/CodeSystem/observation-category|vital-signs SMART scope or a broader version of this scope such as patient/Observation.c. Note that read and search capabilities are already implied by US Core Vital Signs profile.

Servers providing the ability to write FHIR vital sign Observation resources from patient-facing apps SHOULD also support the registration and authorization of apps with the patient/Observation.u?category=http://terminology.hl7.org/CodeSystem/observation-category|vital-signs SMART scope or a broader version of this scope such as patient/Observation.u. Note that systems can support only limited update capabilities.

When offering a patient write capability, health systems may choose to enable or disable this capability based on factors such as the provider, patient, payer, app, and vital type, or may choose to enable the capability broadly. If patients and apps attempting to write data are not enabled, and this can be discerned during the authorization process, the server SHALL omit these unsupported scopes from the resulting access token. If an app uses an access token without the required scopes to submit an Observation or the patient is not enabled to write data, the server SHALL return an error and SHOULD include an OperationOutcome in the response body.

Provider-facing apps

Servers providing the ability to write FHIR vital sign Observation resources from provider-facing apps SHALL support the registration and authorization of apps with the user/Observation.c?category=http://terminology.hl7.org/CodeSystem/observation-category|vital-signs and system/Observation.c?category=http://terminology.hl7.org/CodeSystem/observation-category|vital-signs SMART scopes or broader versions of these scopes such as user/Observation.c and system/Observation.c. Note that read and search capabilities are already implied by US Core Vital Signs profile.

Servers providing the ability to write FHIR vital sign Observation resources from provider-facing apps SHOULD also support the registration and authorization of apps with either user/Observation.u?category=http://terminology.hl7.org/CodeSystem/observation-category|vital-signs and system/Observation.u?category=http://terminology.hl7.org/CodeSystem/observation-category|vital-signs SMART scopes, or broader versions of these scopes such as user/Observation.u and system/Observation.u. Note that systems can support only limited update capabilities.

Configuration

Servers SHALL document supported scopes in the scopes_supported section of a .well-known/smart-configuration capabilities array.

Resource Submission

Servers SHALL support the submission of Observation resources that are not the result of a calculation and validate against a US Core Vital Sign Profile that corresponds to a version used by the server for vital sign Observation read requests.

Servers MAY support the submission of Observation resources that are the result of a calculation (such as the "US Core Pediatric BMI for Age Observation Profile") and validate against a US Core Vital Sign Profile that corresponds to a version used by the server for vital sign Observation read requests.

Servers SHALL respond to supported and valid vital sign Observation creation requests with a status code of 200 OK and a content location header, or with a status code of 202 Accepted. If a content location header is provided, the resources SHALL be visible in subsequent read API calls and accessible within the system in the same manner as other patient-submitted data. If a content location header is not provided, and the server does not subsequently make the resource accessible in read API calls, the server SHALL have a documented and discoverable reason why it was discarded (e.g., a log entry describing rejection during a review workflow or the applicability of a condition in the "Discarding" section below).

Servers SHALL support the creation of a single vital sign through a FHIR create operation, and MAY support the creation of multiple vital signs by submitting a FHIR Batch bundle. When batch creation is supported, clients MAY use this approach to indicate that a set of Observation resources should be reviewed as a group, and systems MAY use this information when sending notifications or displaying the data.

Systems may choose to segregate data that originated from a patient from other vital sign data for the patient (for example, showing it on a separate patient flow sheet).

The workflow for submitted Observations is the responsibility of the receiving system and is out of scope for this version of the guide (e.g., requiring provider review for patient-submitted resources before fully integrating them in the chart).

Observation Elements

meta.tag

• Client - When writing patient-mediated data into the server, provider-facing apps SHALL include a Meta.tag with a system of http://hl7.org/fhir/us/core/CodeSystem/us-core-tags and a value of patient-supplied to indicate that the data was supplied by a patient or patient designee (such as a parent or spouse) rather than by a healthcare provider.
• Server - Systems SHALL associate the patient-supplied tag with vital signs provided by a patient written through this API, and MAY associate the tag with vital signs supplied by a patient regardless of how they arrive in the system. Provider-facing apps writing data supplied by a patient SHALL include this tag in the submitted Observation resources. The server MAY subsequently dissociate the tag from the data through an explicit reconciliation process.

encounter

• Client - If populating this element, apps SHALL use a reference to an Encounter resource in the server, and MAY use the value returned by the launch/encounter SMART scope.
• Server - Systems SHOULD document whether the encounter element is required to create a vital sign. When not required, servers MAY determine this value based on context if it is omitted.

subject

• Client - Apps SHALL populate the subject reference with a reference to a Patient resource in the server. Patient-facing apps SHOULD populate this element based on the value returned as part of the launch/patient SMART scope.

device

• Client - Apps MAY populate the device reference with a reference to the Device resource in the server or a contained Device resource within the Observation. This is the device used to measure the vital sign (e.g., a BP cuff), not the device used to transmit the data (e.g., a phone). Contained device resources SHALL populate at least one deviceName element.
• Server - When this value is populated with a reference to a Device resource on the server, servers SHALL return this reference in subsequent reads operations of the resource that was created. When this value is populated with a reference to a valid contained Device resource, servers MAY ignore the contained Device, return the contained Device as part of subsequent read operations, or create a Device resource in the system and return a reference to it in subsequent read operations. Servers SHALL not return an error due to the presence of a valid contained Device resource. Servers SHOULD document their behavior with regard to contained Device resources.

performer

• Client - Apps SHOULD populate the performer element with a reference to a resource in the server when the resource exists, or the app can create it. For patient-facing apps, if the app knows that a patient collected this data, the app SHALL set the performer to a reference to the patient based on the SMART launch context (this should also match the Observation.subject). If the relevant resource does not exist and the app cannot create it, the app SHOULD populate performer.display.
• Server - When this value is populated in a successful create operation, systems SHALL return it in subsequent read operations of the resource that was created. Note that performer is not currently required in the US Core vital signs profile.

Discarding Observations

For a given vital sign type, if many Observations are submitted with effectiveDateTime or effectivePeriod values that are close in time, a server MAY choose to discard a portion of these Observations or MAY reject submitted Observations with an appropriate OperationOutcome. Systems SHALL clearly document this behavior or the ways in which health systems may customize this behavior in the API documentation.

If a server determines that a vital sign is a duplicate of one it has already stored, the server MAY ignore the Observation or MAY reject the submitted Observation with an appropriate OperationOutcome. Systems SHALL clearly document this behavior or the ways in which health systems may customize this behavior in the API documentation.

Updating Previously Submitted Observations

Servers SHOULD support the ability for patients-facing apps to update the status element of a vital sign resource the user previously wrote to the system from any app to entered-in-error through an update interaction. This capability SHOULD only be used by apps to address data mistakes in data submission.

Including Provenance Information

Servers MAY ignore contained Provenance resources in an Observation being submitted but SHALL not return an error due to their presence.

Resource retrieved from an external organization

When writing an Observation that was retrieved from an external organization (e.g., a health system's EHR or a device manufacturer's cloud data store):

• Apps SHALL pass through any Provenance resources received from the source system, unaltered (except for references, as described below), as contained resources on the Observation. A source system compliant with the US Core FHIR profiles SHOULD include a Provenance resource with agent.type = author that the app can pass through. The app SHALL also pass through resources referenced in elements that are labeled as "Must Support" in the USCDI Provenance profile and populated in the Provenance resources, including them as contained resources in the Observation and updating the references to them.
• When a Provenance resource with agent.type = author is not received from the source system, apps SHALL generate a contained Provenance resource with:
  • recorded set to date and time recorded
  • agent.type = author that has agent.who set to the organization/provider that authored the content, with at least the who.display element populated.
    • When available, a who.identifier.value should be set to the URL where that data was retrieved, and who.identifier.system should be set to urn:ietf:rfc:3986
• Apps MAY include a Provenance resource with agent.type = transmitter with information on the entity that submitted the data. Systems MAY store and display this information and MAY populate this information based on the SMART context associated with the write.

Example:

{
  "resourceType": "Observation",
  "contained": [{
    "resourceType": "Provenance",
    "id": "contained_1",
    "target": [{"reference": "#"}],
    "recorded": "2019-07-09T15:26:23.217+00:00",
    "agent": [{
      "type": {
        "coding": [{
          "system": "http://terminology.hl7.org/CodeSystem/provenance-participant-type",
          "code": "author",
          "display": "Author"
        }]
      },
      "who": {
        "display": "Saint Luke \'s Hospital of Kansas City",
        // identifier could be a URL, as in Patient Access Brands
        "identifier": {
          "system": "urn:ietf:rfc:3986",
          "value": "https://stlukes.example.org"
        }  
      }
    },{
      "type": {
        "coding": [{
          "system": "http://terminology.hl7.org/CodeSystem/provenance-participant-type",
          "code": "transmitter",
          "display": "Transmitter"
        }]
      },
      "who": {
        //this is the user submitting the data
        //can be populated by the EHR based on the SMART context if omitted
        "reference": "Patient/123"
      }
    }]
  }]
  // ... other Observation elements
}

Resources not retrieved from an external organization

When writing an Observation that was not retrieved from an external organization (e.g., transmitted by a home blood pressure cuff or manually entered by a patient):

• Apps MAY include a contained Provenance resource with agent.type = author containing information on the party that wrote the data. Systems MAY store and display this information and MAY populate it based on the SMART context associated with the write.
• Apps MAY include one or more contained Provenance resources with agent.type = composer and agent.type = assembler with information on the device, app, or apps that captured or passed along the data.

Example:

[{
  "resourceType": "Provenance",
  "target": [{"reference": "#"}],
  "recorded": "2019-07-08",
  "agent": [{
    "type": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/provenance-participant-type",
        "code": "composer",
        "display": "Composer"
      }]
    },
    "who": {
      //this is the app that provided the original data
      "display": "OMRON for iOS"
    }
  },{
    "type": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/provenance-participant-type",
        "code": "author",
        "display": "Author"
      }]
    },
    "who": {
      "reference": "Patient/123"
    }
  }]
},{
  "resourceType": "Provenance",
  "target": [{"reference": "#"}],
  "recorded": "2019-07-09T10:26:23.217+00:00",
  "agent": [{
    "type": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/provenance-participant-type",
        "code": "assembler",
        "display": "Assembler"
      }]
    },
    "who": {
      //this is the app that transmits the data
      "display": "Healthkit" 
    }
  }]
}]