FHIR: Fast Healthcare Interoperability Resources
FHIR (HL7 FHIR R4) is the modern standard for healthcare data exchange, using REST-based APIs and standardised resource types to enable real-time, application-level access to clinical data across EHR systems and health IT platforms.
What is FHIR?
Fast Healthcare Interoperability Resources (FHIR, pronounced "fire") is a standard developed by Health Level Seven International (HL7) for exchanging healthcare information electronically. FHIR R4 (released 2019) is the current normative version and the version mandated by CMS and ONC. FHIR uses modern web technologies — RESTful APIs, JSON or XML data formats, and OAuth 2.0 security — making it far more developer-friendly than older HL7 V2 or V3 standards.
FHIR Resource Types
FHIR organises clinical data into "Resources" — discrete, modular units representing specific clinical concepts. Key resource types include:
- Patient: Demographics, identifiers, contact information
- Observation: Lab results, vital signs, clinical assessments (A1C, PHQ-9 score, blood pressure)
- Condition: Diagnoses and problems on the problem list (maps to ICD-10 codes)
- Encounter: Clinical encounters — office visits, hospitalisations, ED visits
- MedicationRequest: Prescriptions and medication orders
- Procedure: Procedures performed (maps to CPT and ICD-10-PCS codes)
- Claim: Billing claims and claim responses
CMS Interoperability Rule and FHIR Mandates
The CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F, 2024) requires Medicare Advantage, Medicaid, and CHIP plans to implement FHIR R4-based APIs for: Patient Access API (patient access to their claims and clinical data), Provider Directory API, and — crucially for prior authorisation — a Prior Authorization API that automates PA requests and decisions. These requirements took effect January 2027 for PA APIs.
FHIR API vs CSV Export for Analytics
A common misconception is that FHIR API integration is the only way to achieve interoperability for analytics purposes. In practice, structured CSV/flat-file exports from EHRs — when properly specified and systematically delivered — are functionally equivalent for population health analytics and often significantly more complete and reliable than FHIR API implementations, which vary in data completeness by EHR vendor. The interoperability goal is structured, accessible data; the mechanism is less important than the data quality.