Fast Healthcare Interoperability Resources (FHIR)

FHIR decomposes healthcare data into discrete, modular components called Resources. Each resource represents a specific clinical or administrative concept—such as a Patient, Observation, MedicationRequest, or Condition—with a well-defined structure and unique URL endpoint.

• Resources are the smallest unit of exchange, enabling granular data access
• Each resource contains structured data elements, narrative text for human readability, and metadata tags
• Common resources include AllergyIntolerance, Procedure, DiagnosticReport, and CarePlan
• Extensions allow implementers to add custom data elements without breaking the base specification

FHIR leverages standard HTTP protocols and RESTful architectural patterns to enable interoperability through familiar web paradigms. Every resource is accessible via a predictable URL endpoint using standard HTTP verbs.

• GET retrieves resources; POST creates new instances; PUT updates existing records; DELETE removes resources
• Search operations use query parameters like GET /Patient?name=Smith&birthdate=1970
• Responses are returned in JSON, XML, or RDF formats, with JSON being the most common for modern development
• Stateless interactions simplify scalability and align with cloud-native architectures

The Substitutable Medical Applications and Reusable Technologies (SMART) platform builds on FHIR to provide a standardized framework for launching third-party applications within EHR systems. This enables a plug-and-play ecosystem of interoperable clinical tools.

• Uses OAuth 2.0 and OpenID Connect for secure authorization and authentication
• Supports both provider-facing and patient-facing applications via the same API
• SMART App Launch defines how apps are discovered, authorized, and launched from within an EHR session
• Enables a marketplace model where health systems can adopt best-of-breed applications without custom integration

FHIR's base specification is intentionally generic. Implementation Guides (IGs) and Profiles constrain and adapt the standard for specific use cases, jurisdictions, or domains. This balances global interoperability with local requirements.

• US Core IG defines the minimum conformance requirements for U.S. EHR systems under the 21st Century Cures Act
• Profiles constrain cardinality, terminology bindings, and extensions for specific contexts
• The Argonaut Project accelerated FHIR adoption by defining pragmatic profiles for common clinical scenarios
• International guides like IPS (International Patient Summary) enable cross-border data exchange

FHIR resources achieve semantic interoperability by binding data elements to standardized code systems. This ensures that a 'diagnosis' means the same thing across different systems and organizations.

• Strong bindings to SNOMED CT for clinical findings, LOINC for laboratory observations, and RxNorm for medications
• ValueSet resources define allowed code collections for specific contexts
• ConceptMap resources enable translation between different code systems
• Terminology servers provide runtime validation and code lookup via FHIR APIs

Beyond basic CRUD interactions, FHIR defines Operations for complex server-side logic and Bulk Data Access for population-level analytics. These extensions address use cases that simple REST endpoints cannot handle.

• $validate checks resource conformance against profiles without persisting data
• $match performs probabilistic patient matching for record linkage
• Bulk FHIR enables asynchronous export of entire patient populations using the FHIR Bulk Data Access IG
• Supports flat file formats like NDJSON for efficient processing of millions of records

An open, standards-based technology platform that enables developers to create substitutable, interoperable medical applications that run seamlessly across different electronic health record systems using the FHIR API and OAuth 2.0 for authentication.

• Launches third-party apps from within the EHR interface
• Defines scopes for granular patient data access
• Enables a plug-and-play app ecosystem similar to a smartphone