FHIR SDC API

This article outlines operations from the FHIR SDC Implementation Guide.

Implementation corresponds to SDC FHIR IG - 3.0.version 0

FHIR SDC API

Aidbox Forms module supports FHIR SDC operations:

• $populate - filling out a form with existing data (FHIR)

• $populatelink - filling out a form with existing data, and return signed link to it (FHIR)

• $extract - extract data from QuestionnaireResponse to other FHIR resources (FHIR)

• $expand - create a simple collection of codes suitable for use for data entry or validation. (FHIR)

We have created an Aidbox notebook demonstrating different population and extraction methods:

Aidbox forms: populate & extract

Populate Questionnaire - $populate

The populate operation generates a QuestionnaireResponse based on a specific Questionnaire, filling in answers to questions where possible based on information provided as part of the operation or already known by the server about the subject of the Questionnaire.

This implementation supports the Observation based and Expression based population methods.

URLs

POST [base]/fhir/Questionnaire/$populate

POST [base]/fhir/Questionnaire/[id]/$populate

Parameters

Parameter	Cardinality	Type	Status
identifier	0..1	Identifier	supported
canonical	0..1	uri	supported
questionnaire	0..1	Questionnaire	supported
questionnaireRef	0..1	Reference	supported
subject	1..1	Reference	supported
context	0..*	Reference	supported
context.name	1..1	string	supported
context.content	1..*	Reference	supported
local	0..1	boolean	supported
launchContext	0..1	Extension	not supported

Parameters are specified via FHIR Parameters type.

Example

resourceType: Parameters
parameter:
- name: subject
  valueReference:
    reference: Patient/pt-1

identifier

A logical questionnaire identifier (i.e. Questionnaire.identifier). The server must know the questionnaire or be able to retrieve it from other known repositories.

name: identifier
valueIdentifier:
  system: 'forms.aidbox'
  value: 'vitals'

canonical

The canonical identifier for the questionnaire (optionally version-specific).

name: canonical
valueCanonical: http://forms.aidbox.io/Questionnaire/vitals

questionnaire

The Questionnaire is provided directly as part of the request. Servers may choose not to accept questionnaires in this fashion

name: questionnaire
resource:
  resourceType: Questionnaire
  id: new-form
  title: "Vitals"
  ...

questionnaireRef

The Questionnaire is provided as a resource reference. Servers may choose not to accept questionnaires in this fashion or may fail if they cannot resolve or access the referenced questionnaire.

name: questionnaireRef
valueReference:
  resourceType: Questionnaire
  id: new-form

subject

The resource that is to be the QuestionnaireResponse.subject. The QuestionnaireResponse instance will reference the provided subject. In addition, if the local parameter is set to true, server information about the specified subject will be used to populate the instance.

name: subject
valueReference:
  reference: Patient/pt-1

local

If specified and set to true (and the server is capable), the server should use what resources and other knowledge it has about the referenced subject when pre-populating answers to questions.

name: local
valueBoolean: true

context

Resources containing information to be used to help populate the QuestionnaireResponse. These will typically be FHIR resources.

Context paramertes are presented as pairs of name and content parameters that are placed under the part key.

They should correspond launchContext parameter definitions.

name: context
part:
- name: name
  valueString: encounter
- name: content
  valueReference:
    reference: Encounter/enc1

FHIR SDC launchContext extension enumerates possible context variables, they are:

Code	Type	Definition
patient	Reference/resource	Patient Patient in context at launch time
encounter	Reference/resource	Encounter context at launch time
location	Reference/resource	Location context at launch time
user	Reference<Patient, Device, PractitionerRole, Practitioner, RelatedPerson, Organization>/resource	User in context at launch time
study	Reference/resource	ResearchStudy in context at launch time

Additionnaly Aidbox expands this list with parameters that mirrors QuestionnaireResponse root properties.

WARN: This is non FHIR SDC compliant behavior!

Paramerters passed directly to QuestionnaireResponse root properties and should not be used in populate expressions.

Code	Type
identifier	Identifier
basedOn	Reference<CarePlan, ServiceRequest>
partOf	Reference<Observation, Procedure>
encounter	Reference<CarePlan/ServiceRequest>
author	Reference<Device, Practitioner, PractitionerRole, Patient, RelatedPerson, Organization>
source	Reference<Device, Organization, Patient, Practitioner, PractitionerRole, RelatedPerson>

Example:

name: name
valueReference:
  reference: ServiceRequest/sr1

context.name

The name of the launchContext or root Questionnaire variable the passed content should be used as for population purposes. The name SHALL correspond to a launchContext or variable delared at the root of the Questionnaire.

name: name
valueString: encounter

context.content

The actual resource (or resources) to use as the value of the launchContext or variable.

name: content
valueReference:
  reference: Encounter/enc1

Or

name: content
resource:
  ...
  resourceType: Encounter
  id: enc1
  subject:
    reference: Patient/pt-1
  ...

launchContext

Resources that provide context for form processing logic (pre-population) when creating/displaying/editing a QuestionnaireResponse.

Response

• in failure case - response is specified as OperationOutcome object.
• in success case - response is specified as Parameters object.

Success response shape

Parameter	Cardinality	Type	Description
response	1..1	QuestionnaireResponse	The partially (or fully)-populated set of answers for the specified Questionnaire
issues	0..1	OperationOutcome	A list of hints and warnings about problems encountered while populating the questionnaire.

Usage Example

Request

POST [base]/fhir/Questionnaire/vitals/$populate
content-type: text/yaml

resourceType: Parameters
parameter:
- name: subject
  valueReference:
    reference: Patient/pt-1
- name: context
  part:
  - name: name
    valueString: encounter
  - name: content
    valueReference:
      reference: Encounter/enc1

Success Response

HTTP status: 200

resourceType: Parameters
parameter:
- name: response
  resource:
    resourceType: QuestionnaireResponse
    questionnaire: http://aidbox.app/forms/new-form
    status: in-progress
    basedOn:
      reference: ServiceRequest/sr1
    encounter:
      reference: Encounter/enc1
    item:
    - linkId: name
      text: Name
    - linkId: weight

Failure Response

HTTP status: 422

resourceType: OperationOutcome
text:
  status: generated
  div: Parameters are invalid
issue:
- severity: error
  code: invalid
  expression:
  - parameter.0.resource
  diagnostics: unknown key :resource

Populate Questionnaire and generate a link - $populatelink

The populatelink operation generates a link to a web page to be used to answer a specified Questionnaire. The form at the specified location will be pre-filled with answers to questions where possible based on information provided as part of the operation or already known by the server about the subject of the Questionnaire.

URLs

POST [base]/fhir/Questionnaire/$populatelink

POST [base]/fhir/Questionnaire/[id]/$populatelink

Parameters

The base set of parameters is the same as for $populate. On top of that, a few extra parameters are supported by Aidbox Forms.

WARN: The following parameters are not FHIR SDC compliant. This is an extension of the specification.

NOTE: Don't forget to wrap parameters in Parameters object

resourceType: Parameters
parameter:
- name:  [var-name]
  valueX: [varType: var-value]

Parameter	Cardinality	Type
allow-amend	0..1	Boolean
allow-repopulate	0..1	Boolean
redirect-on-submit	0..1	String
redirect-on-submit	0..1	String
expiration	0..1	Integer
theme	0..1	String
config	0..1	String
read-only	0..1	Boolean
app-name	0..1	String

allow-amend

Whether the generated link will allow amending and re-submitting the form.

name: allow-amend
valueBoolean: true

allow-repopulate

Whether the generated link will allow re-populating the form.

NOTE: Repopulate will be working only with forms that contain populate behavior

name: allow-repopulate
valueBoolean: true

redirect-on-submit

A URL where the user will be redirected to after successfully submitting the form.

name: redirect-on-submit
valueString: https://example.com/submit-hook?questionnaire=123

redirect-on-save

A URL where the user will be redirected to after hitting Save button.

By default Save button is not visible - form autosaved after every keystroke. But sometimes it's usefull to close form in a partially-filled state

name: redirect-on-save
valueString: https://example.com/submit-hook?questionnaire=123

link expiration time

Link expiration period (days)

name: expiration
valueInteger: 30

By default thir parameter = 7 days

theme

Form theme. QuestionnaireTheme resource id.

name: theme
valueString: hs-theme

config

Form config. SDCConfig resource id.

name: theme
valueString: default-config

read-only

Open form in read-only mode.

name: read-only
valueBoolean: true

app-name

Application name that will be used in Audit logging when returned link was used.

Audit logging should be enabled.

name: app-name
valueString: my-app

Response

• in failure case - response is specified as OperationOutcome object containing a link.
• in success case - response is specified as Parameters object containing a list of issues.

Parameter	Cardinality	Type	Description
link	1..1	uri	The URL for the web form that supports capturing the information defined by questionnaire
issues	0..1	OperationOutcome	A list of hints and warnings about problems encountered while populating the questionnaire

Usage Example

Request

POST [base]/fhir/Questionnaire/vitals/$populatelink
content-type: text/yaml

resourceType: Parameters
parameter:
- name: subject
  valueReference:
    reference: Patient/pt-1
- name: context
  part:
  - name: name
    valueString: encounter
  - name: content
    resource:
      resourceType: Encounter
      id: enc-1
      subject:
        reference: Patient/pt-1

Success Response

HTTP status: 200

resourceType: Parameters
parameter:
- name: link
  valueUri: http://forms.aidbox.io/ui/sdc#/questionnaire-response/12c1178c-70a9-4e02-a53d-65b13373926e?token=eyJhbGciOiJIUzI

Failure Response

HTTP status: 422

resourceType: OperationOutcome
text:
  status: generated
  div: Parameters are invalid
issue:
- severity: error
  code: invalid
  expression:
  - parameter.0.resource
  diagnostics: unknown key :resource

Questionnaire response extract to resources - $extract

The extract operation takes a completed QuestionnaireResponse and extracts it's data to Bundle of resources by using metadata embedded in the Questionnaire the QuestionnaireResponse is based on. The extracted resources might include Observations, MedicationStatements and other standard FHIR resources which can then be shared and manipulated.

Aidbox supports only the Observation based and Definition based extraction methods.

Current Logic for Observation-based extraction:

• A new Observation is created for each Questionnaire Response instance at the time of data extraction.

• If a QR is amended (modified after submission), the existing Observations linked to that QR are updated accordingly.

In the future, Aidbox Forms will align with the implementation described in the FHIR Structured Data Capture (SDC) specification.

Current Logic for Definition-based extraction:

• Two Options for Resource Extraction:

  • New Resource: If "new resource" is selected, a new resource is always created during extraction.

  • Existing Resource: If "existing resource" is selected, the system includes the questionnaire-itemExtractionContext extension. This extension can be added either at the root of the Questionnaire or at any item level. It identifies the resource that serves as the context for extraction.

Using itemExtractionContext:

• Empty itemExtractionContext: When the itemExtractionContext is empty, the Questionnaire is used to create a new resource.

• Populated itemExtractionContext: If the itemExtractionContext contains a resource (or set of resources), the Questionnaire updates the existing resource.

URLs

URL: [base]/fhir/QuestionnaireResponse/$extract

URL: [base]/fhir/QuestionnaireResponse/[id]/$extract

Parameters

Parameter	Cardinality	Type	Description
questionnaire-response	0..1	Resourse	The QuestionnaireResponse to extract data from.

Parameters are specified via FHIR Parameters type.

Example

resourceType: Parameters
parameter:
- name: questionnaire-response
  resource:
    id: qr-1
    resourceType: QuestionnaireResponse
    ...

Response

• in failure case - response is specified as OperationOutcome object.
• in success case - response is specified as Parameters object.

Parameter	Cardinality	Type	Description
return	1..1	Resourse	FHIR Bundle with extracted resources
issues	0..1	OperationOutcome	A list of hints and warnings about problems encountered while extracting the data

Usage Example

Request

POST [base]/fhir/QuestionnaireResponse/$extract
content-type: text/yaml

resourceType: Parameters
parameter:
- name: questionnaire-response
  resource:
    id: pt-1
    resourceType: QuestionnaireResponse
    questionnaire: https://forms.aidbox.io/vitals
    item:
      - linkId: temperature
        valueDecimal: 36.6
    ...

Success Response

HTTP status: 200

return:
  resourceType: Bundle
  type: transaction
  entry:
  - resource:
      resourceType: Observation
      status: final
      code:
        coding:
        - code: body-temperature
          system: loinc
      subject:
        reference: Patient/pt-1
      valueQuantity:
        unit: [c]
        value: 36.6
    request: {method: POST,  url: /Observation}

Failure Response

HTTP status: 422

resourceType: OperationOutcome
text:
  status: generated
  div: Parameters are invalid
issue:
- severity: error
  code: invalid
  expression:
  - parameter.0.resource.given
  diagnostics: unknown key :given

ValueSet Expansion - $expand

Value Sets are used to define possible coded answer choices in a questionnaire.

The use of standardized codes is useful when data needs to be populated into the questionnaire or extracted from the questionnaire for other uses.

The expand operation expand given ValueSet in to set of concepts.

This operation is described in detail here.