HL7 v2

HL7 v2
Name	Health Level Seven Version 2
Acronym	HL7 v2
Developer	Health Level Seven International
Initial release	1989
Latest release	2.9 (2019)
Status	Widely used
Domain	Healthcare information exchange

HL7 v2 is a widely adopted messaging standard for exchanging clinical and administrative data between healthcare systems. It was developed to enable interoperability among disparate Centers for Medicare and Medicaid Services, Department of Veterans Affairs, Mayo Clinic, Kaiser Permanente, and other large National Health Service-level and institutional health information systems. The specification balances flexibility and pragmatism, allowing vendors such as Epic Systems Corporation, Cerner Corporation, Allscripts, Siemens Healthineers, and GE Healthcare to implement interfaces that connect laboratory, radiology, electronic health record, and billing systems.

History and Development

Development began in the late 1980s under the auspices of Health Level Seven International, an organization founded to address communication problems among healthcare information systems. Early contributors included vendors and academic centers like Intermountain Healthcare, Partners HealthCare (now Mass General Brigham), and federal agencies such as Centers for Medicare and Medicaid Services and the Veterans Health Administration. Over successive releases the standard incorporated input from international standards bodies and projects including ISO, ANSI, and regional efforts like Canadian Institute for Health Information initiatives. The iterative model produced versions 2.0 through 2.9, with stakeholder-driven changes influenced by implementers at institutions such as Johns Hopkins Hospital and Cleveland Clinic and initiatives from consortia like Integrating the Healthcare Enterprise.

Standard Structure and Message Types

The specification defines a message-based architecture organized into messages and segments used across clinical domains at organizations such as World Health Organization, Centers for Disease Control and Prevention, and national health agencies. Core message types address administrative workflows implemented by providers like Mount Sinai Health System and payers such as Blue Cross Blue Shield Association. Common message types include patient administration messages used by registration systems at Stanford Health Care, laboratory reporting messages consumed by public health entities like Public Health England, and observation/result messages used by reference labs like Quest Diagnostics. Message types are standardized for interoperability across vendors including Oracle Cerner and MEDITECH.

Encoding Rules and Segments

Messages are composed of ordered segments, each segment containing fields, components, and subcomponents used by software from vendors such as Philips Healthcare and Roche Diagnostics. The MSH segment provides envelope metadata and is followed by segments like PID, OBR, OBX, and PV1 that carry identity, order, observation, and visit information respectively—elements used in workflows at institutions like Boston Children's Hospital and UCLA Health. Encoding rules permit both delimited and escape-encoded values to represent complex data drawn from clinical labs at Laboratory Corporation of America or imaging centers affiliated with Mount Sinai. Segment definitions evolved to support identifiers from systems like National Provider Identifier registries and terminology bindings from SNOMED International, LOINC, and ICD-10 used by public and private payers.

Implementation and Interoperability

Implementers at major vendors and health systems often create interface engines—products of companies like Mirth Corporation and Informatica—to route and transform messages between electronic health record systems at NewYork-Presbyterian Hospital and ancillary systems at Children's Hospital of Philadelphia. Integration patterns incorporate mapping tools and middleware frameworks used by consulting firms such as Accenture and Deloitte to achieve interoperability across networks like CommonWell Health Alliance and Carequality. Interoperability initiatives from governments and alliances, including programs run by Office of the National Coordinator for Health Information Technology and national health services, routinely reference the standard as a pragmatic bridge for legacy systems while migration strategies often involve translation to newer standards supported by HL7 FHIR and other standards organizations.

Versioning and Conformance Testing

The versioning scheme spans multiple minor and major releases with backward-compatibility guidance adopted by vendors and institutions including Partners HealthCare and Geisinger Health System. Conformance profiles are produced by implementation guides from organizations such as IHE and national authorities; testing programs are run by conformance labs and interoperability testing events sponsored by HIMSS and standards bodies like Health Level Seven International. Certification programs from national agencies and accrediting organizations use test suites that validate message syntax, segment cardinality, and coded value sets as practiced by large providers and vendors, ensuring that systems deployed at hospitals like Cleveland Clinic meet operational criteria.

Use Cases and Adoption in Healthcare

The standard underpins use cases across clinical care, public health, and administration: patient registration and admission-discharge-transfer workflows implemented in hospitals like Mount Sinai; laboratory and microbiology result reporting used by reference labs such as Quest Diagnostics; radiology order and report exchange practiced in imaging centers operated by Radiology Partners; and billing and claims coordination between providers and insurers like Aetna. Global adoption spans regional health authorities in countries such as United Kingdom, Canada, Australia, and Germany, where the standard integrates legacy systems and supports national reporting requirements tied to organizations like World Health Organization and European Centre for Disease Prevention and Control.

Category:Healthcare standards