By Medical form

SDC vs FHIR Composition: Which Fits Structured Clinical Notes

SDC vs FHIR Composition: Which Fits Structured Clinical Notes

Structured clinical notes sit at an architectural crossroads in FHIR. One path captures the note as a SDC-backed Questionnaire and stores the result as a QuestionnaireResponse, optionally extracted into discrete clinical resources. The other path captures the note as a FHIR Composition, organized into sections that reference Observations, Conditions, and other resources directly. Both produce structured output. The choice between them is consequential for downstream search, validation, and clinical decision support. For broader background, see the FHIR comparison index.

The FHIR SDC form builders reference guide covers the broader picture in which this comparison sits.

What Each Resource Is For

SDC and QuestionnaireResponse are designed for data capture. The Questionnaire defines what to ask; the QuestionnaireResponse holds the answers. The shape is question-and-answer, structured around linkId. Extraction from QuestionnaireResponse into other FHIR resources is a separate step.

FHIR Composition is designed for document-shaped clinical content. The Composition has sections, each section references clinical resources, and the whole thing forms a document that can be signed, attested, and exchanged as a clinical note. The shape is hierarchical and document-oriented, not question-oriented.

The two resources solve overlapping but distinct problems. SDC excels at structured intake and assessment forms; Composition excels at signed clinical documents like discharge summaries and visit notes.

When SDC Fits Better

SDC and QuestionnaireResponse are the right choice when:

  1. The note is captured through a question-and-answer flow, like a depression screening, a symptom assessment, or a procedure-specific checklist.
  2. Validation against a defined schema matters, since the Questionnaire definition acts as a contract for what shape the response must take.
  3. Conditional logic, calculated fields, and value-set-bound answers are part of the data-capture flow.

The top FHIR form builders for clinical trial research walkthrough covers a use case where SDC almost always wins.

When Composition Fits Better

FHIR Composition is the right choice when:

  1. The note is a clinical document with sections, intended to be signed and stored as a document of record.
  2. The downstream consumers expect a CDA-style structure that they can render as a readable narrative.
  3. The note aggregates references to existing clinical resources rather than introducing new structured fields.

Visit notes, discharge summaries, and operative reports lean toward Composition. Intake forms and assessments lean toward SDC.

The Hybrid Pattern

In practice, both resources show up in the same clinical workflow. The intake form is a Questionnaire; the resulting QuestionnaireResponse is extracted into Observations; the visit note is a Composition that references those Observations and adds free-text narrative. The two resources complement each other when the architecture treats them as different tools for different jobs rather than competing options for the same job.

Teams that try to force everything through one resource type usually end up with awkward outputs. Composition-only stacks struggle with assessment forms; SDC-only stacks struggle with signed clinical documents.

For the broader question of how to land form data in the right shape from day one, the QuestionnaireResponse vs custom JSON comparison covers the related architectural decision that often precedes this one.

The honest framing is that SDC and Composition are not competitors. They are different layers of the clinical data stack, and the question is which one fits the specific capture pattern at hand. The honest signal is operational fit, not feature breadth; the engine that disappears into the stack is the one that earned its place.

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