SDC form builders range from lightweight demos to production-grade platforms. Seven capabilities separate the ones that ship from the ones that struggle.
1. Full enableWhen and enableWhenExpression support. Basic single-condition and complex FHIRPath expression variants. Renderers without expression support break on real intake logic.
2. Calculated expressions. calculatedExpression extension for auto-computed answers (BMI from height/weight, PHQ-9 total from item scores).
3. Server-side $extract. SDC IG's `$extract` converts QuestionnaireResponse into structured resources server-side. Reduces client complexity.
4. Pre-population from FHIR resources. Pull Patient, Observation, existing Condition into the form on load.
5. Save-and-resume with versioning. ETag-based conflict detection for concurrent editing.
6. Multi-language support. Designations for translated question and choice labels.
7. Accessibility (WCAG 2.1 AA). Keyboard navigation, screen reader labels, sufficient color contrast.
Vendor scorecard (mid-2026)
| Builder | enableWhenExpression | Calculated | $extract |
Pre-population | Multi-language | WCAG |
|---|---|---|---|---|---|---|
| Aidbox Formbox | Full | Full | Full | Full | Full | Yes |
| LHC-Forms | Full | Full | Full | Full | Full | Yes |
| Smile CDR SDC | Full | Full | Both | Full | Partial | Yes |
| NLM Form Builder | Authoring | Authoring | N/A | N/A | Yes | Yes |
| Firely SDC.NET | Full | Partial | Full | Full | Partial | Yes |
Selection is a fit question: pick against the specific capability requirements your Questionnaire needs, not against the marketing checkbox.