HL7

HL7, or Health Level Seven International, is a not-for-profit organization that develops standards for the exchange, integration, sharing, and retrieval of electronic health information. Founded in 1987, HL7 aims to enable interoperability among diverse healthcare systems by providing a common framework for transmitting clinical and administrative data. The organization maintains a family of standards used worldwide by hospitals, laboratories, clinics, and health information exchanges.

The best known HL7 standards are HL7 v2.x, HL7 v3, and HL7 FHIR. HL7 v2.x is a widely deployed messaging standard that encodes data in segment-based, delimited messages; it supports events such as admissions, orders, results, and patient demographics but allows significant variability across implementations. HL7 v3 introduced a formal Reference Information Model and uses XML encoding, but its adoption has been more limited due to complexity. HL7 FHIR (Fast Healthcare Interoperability Resources) is a newer approach that uses modern web technologies, including RESTful APIs, JSON and XML representations, and a modular resource model. FHIR emphasizes ease of implementation and extensibility, with profiles and mappings to support interoperability across systems. The HL7 CDA (Clinical Document Architecture) and related Continuity of Care Document (CCD) are document-centric standards used for structured clinical documents in XML.

HL7 standards are developed through a consensus-driven process involving member organizations, work groups, and public balloting, and are accompanied by implementation guides and conformance testing. They are used to support interoperability across the health IT ecosystem, enabling exchanges such as patient demographics, orders and results, clinical documentation, and health information exchanges. HL7 standards are adopted internationally and continue to evolve, with FHIR representing a move toward web-based, interoperable data exchange suitable for modern health apps and EHR ecosystems.