From HL7 to FHIR: The Interoperability Journey and Why It Matters Now

• GHIT Digital
• October 7, 2025
• GHIT Digital Insights
• 0 Comments

From HL7 to FHIR: The Interoperability Journey and Why It Matters Now

For Payers (P1), Providers (P2), Pharma / Life Sciences / Medical Devices (P3)

1. 1. Executive Summary

Healthcare interoperability has evolved from HL7 v2 pipelines to FHIR-based APIs. Modern healthcare demands real-time, app-driven, API-first data exchange. Strategic interoperability is essential for care continuity, regulatory compliance, analytics, and real-world evidence generation.

1. 2. HL7: The Foundation of Clinical Interoperability

   1. 2.1 HL7 v2 Growth

• – Lightweight, text-based protocol (pipe-delimited).
• – Event-driven: ADT, ORU, ORM, DFT, MDM.
• – Asynchronous messaging with ACK/NACK.
• – Ubiquitous in EHRs, labs, radiology, devices.

  1. 2.2 Limitations

• – Hard to orchestrate and scale for multi-consumer ecosystems.
• – No query model; dependent on event pushes.
• – Semantic inconsistencies (custom Z-segments).
• – Poor web/REST integration; JSON/modern formats absent.

HL7 was a hero of its time, but 21st-century digital healthcare exposed its limits.

1. 3. FHIR: The API-First Future

• – Resource-oriented model (Patient, Observation, Encounter, Claim).
• – RESTful APIs with JSON/XML support.
• – Profiles & constraints (US Core, CARIN) ensure standardization.
• – Security via SMART on FHIR, OAuth2, OpenID Connect.
• – Provenance, versioning, extensions for traceability.

Timeline: DSTU 1 → R4 → regulatory push → cloud adoption (AWS, Azure, Google Health API).

1. 4. Why Interoperability Matters Now

Drivers for P1/P2/P3 with examples:

1. 5. HL7 + FHIR: Bridging Generations

Hybrid architecture pattern:

• 1. Legacy HL7 pipelines remain for mission-critical flows.
• 2. Canonical FHIR repository (FPDR) layers on top.
• 3. Integration engine ingests HL7 → FHIR.
• 4. Expose SMART on FHIR endpoints for apps, analytics, partner systems.
• 5. Gradual migration of new integrations directly to FHIR.
• 6. Governance ensures stability and compliance.

1. 6. Use Cases

• 1. Cross-organization patient summary (P2 + P3)
  • – HL7: CCD/CCDA transfers
  • – FHIR: GET /Patient/{id}/$everything → normalized data
  • – Benefit: continuity, fewer errors, smoother transitions

• 2. Consumer access to claims + clinical (P1)
  • – HL7: custom glue required
  • – FHIR: FPDR + SMART app → unified, real-time view
  • – Benefit: regulatory compliance, better UX

• 3. Real-world evidence / clinical trial data (P3)
  • – HL7: scattered, inconsistent data
  • – FHIR: bulk queries / subscription → normalized RWE
  • – Benefit: consistent longitudinal data for analysis

• 4. Provider-payer coordination (P1 + P2)
  • – HL7: faxes, batch files
  • – FHIR: Task / communication resources → proactive, closed-loop care
  • – Benefit: tighter care coordination, reduced friction

1. 7. Architecture & Technical Patterns

• – Hybrid HL7 + FHIR
• – Event-driven subscriptions, bulk data export, SMART app integration
• – Security: OAuth2 scopes, access auditing
• – Governance: version control, semantic validation

1. 8. Strategic Implications & Recommendations

Faster onboarding, AI/analytics readiness, compliance, improved patient/provider experience

• Recommended steps:
  •   1. Adopt hybrid HL7 + FHIR architecture
  •   2. Implement canonical FHIR repository
  •   3. Build SMART-on-FHIR enabled apps
  •   4. Leverage cloud FHIR platforms
  •   5. Enforce governance and continuous monitoring

1. 9. Conclusion

HL7 and FHIR complement each other. Organizations that adopt this hybrid approach gain operational, regulatory, and clinical advantages across payers, providers, and life sciences.

• Monika Vashishtha, MBA I President:     Monika@GHIT.digital  I 646.734.6482