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Health Level 7


Health Level Seven (HL7), is an all-volunteer, not-for-profit organization involved in development of international healthcare standards. “HL7” is also used to refer to some of the specific standards created by the organization (i.e. HL7 v2.x, v3.0, HL7 RIM etc.).
HL7 and its members provide a framework (and related standards) for the exchange, integration, sharing and retrieval of electronic health information. v2.x of the standards, which support clinical practice and the management, delivery, and evaluation of health services, are the most commonly used in the world.

Organization Origin

HL7 is an international community of healthcare subject matter experts and information scientists collaborating to create standards for the exchange, management and integration of electronic healthcare information.

HL7 promotes the use of such standards within and among healthcare organizations to increase the effectiveness and efficiency of healthcare delivery for the benefit of all.
The HL7 community is organized in the form of a global organization (Health Level Seven, Inc.) and country-specific affiliate organizations.

  • Health Level Seven, Inc. (HL7, Inc. ) is headquartered in Ann Arbor, Michigan, U.S.
  • HL7 affiliate organizations, not-for-profit organizations incorporated in local jurisdictions, exist in over 40 countries. The first affiliate organization was created in Germany in 1993.


The organizational structure of HL7 Inc. is as follows:

  • The organization is managed by a Board of Directors, which comprises 10 elected positions and three appointed positions.
  • The Chief Executive Officer (currently Charles Jaffe, MD, PhD) serves as an ex officio member of and reports to the Board of Directors. The Chief Technology Officer (currently John Quinn); and the Chief Operations Officer (currently Mark McDougall) report to the CEO and also serve as ex officio members on the Board of Directors.
  • Members of HL7 are known collectively as “The Working Group”. The Working Group is responsible for defining the HL7 standard protocol and is composed of Standing Administrative Committees and Working Groups.
  • Standing Administrative committees focus on organizational or promotional activities, such as Education, Implementation, Marketing, Outreach Committee for Clinical Research, Publishing and Process Improvement and Tooling.
  • Working groups are directly responsible for the content of the Standards, framing the actual language of the specifications.



HL7 was founded in 1987 to produce a standard for hospital information systems. HL7, Inc. is a standards organization that was accredited in 1994 by the American National Standards Institute (ANSI).

HL7 is one of several American National Standards Institute (ANSI) -accredited Standards Developing Organizations (SDOs) operating in the healthcare arena. Most SDOs produce standards (sometimes called specifications or protocols) for a particular healthcare domain such as pharmacy, medical devices, imaging or insurance (claims processing) transactions. Health Level Seven’s domain is clinical and administrative data.
Today, HL7 has been adopted by several national SDOs outside the U.S. Those SDOs are consequently not accredited by ANSI. However, HL7 is now adopted by ISO as a centre of gravity in international standardization and accredited as a partnering organization for mutual issuing of standards. The first mutually published standard is ISO/HL7 21731:2006 Health informatics -- HL7 version 3 -- Reference information model -- Release 1.


The Name "Health Level-7"

The name "Health Level-7" is a reference to the seventh "application" layer of the ISO OSI Reference model. The name indicates that HL7 focuses on application layer protocols for the health care domain, independent of lower layers. HL7 effectively considers all lower layers merely as tools.

HL7 collaborates with other standards development organizations and national and international sanctioning bodies (e.g. ANSI and ISO), in both the healthcare and information infrastructure domains to promote the use of supportive and compatible standards. HL7 collaborates with healthcare information technology users to ensure that HL7 standards meet real-world requirements, and that appropriate standards development efforts are initiated by HL7 to meet emergent requirements.
About 45% of the global membership (of either HL7 Inc. or an HL7 affiliate) is located in Europe, 35% in North America, 15% in Asia-Oceania and 5% elsewhere.



HL7 Standards
Hospitals and other healthcare provider organizations typically have many different computer systems used for everything from billing records to patient tracking. All of these systems should communicate with each other (or "interface") when they receive new information but not all do so. HL7 specifies a number of flexible standards, guidelines, and methodologies by which various healthcare systems can communicate with each other. Such guidelines or data standards are a set of rules that allow information to be shared and processed in a uniform and consistent manner. These data standards are meant to allow healthcare organizations to easily share clinical information. Theoretically, this ability to exchange information should help to minimize the tendency for medical care to be geographically isolated and highly variable.
HL7 develops Conceptual Standards (i.e. HL7 RIM), Document Standards (i.e. HL7 CDA), Application Standards (i.e. HL7 CCOW) and Messaging Standards (i.e. HL7 v2.x and v3.0). Messaging standards are particularly important because they define how information is packaged and communicated from one party to another. Such standards set the language, structure and data types required for seamless integration from one system to another.
HL7 encompasses the complete life cycle of a standards specification including the development, adoption, market recognition, utilization, and adherence. Access to the HL7 standards requires paid membership of HL7 Inc. or one of its affiliates.

HL7 Version 2.x
The HL7 version 2 standard has the aim to support hospital workflows. It was originally created in 1987.

V2.x Messaging
HL7 version 2 defines a series of electronic messages to support administrative, logistical, financial as well as clinical processes. Since 1987 the standard has been updated regularly, resulting in versions 2.1, 2.2, 2.3, 2.3.1, 2.4, 2.5, 2.5.1 and 2.6. Collectively these versions are known as version 2.x. The v2.x standards are backwards compatible, i.e. a message based on version 2.3 will be understood by an application that supports version 2.6.
HL7 v2.x mostly uses a textual, non-XML encoding syntax based on delimiters.
HL7 v2.x has allowed for the interoperability between electronic Patient Administration Systems (PAS), Electronic Practice Management (EPM) systems, Laboratory Information Systems (LIS), Dietary, Pharmacy and Billing systems as well as Electronic Medical Record (EMR) or Electronic Health Record (EHR) systems. Currently, HL7’s v2.x messaging standard is supported by every major medical information systems vendor in the United States

HL7 Version 3

The HL7 version 3 standard has the aim to support any and all healthcare workflows. Development of version 3 started around 1995, resulting in an initial standard publication in 2005. The v3 standard, as opposed to version 2, is based on a formal methodology (the HDF) and object oriented principles.

RIM - ISO/HL7 21731
The Reference Information Model (RIM) is the cornerstone of the HL7 Version 3 development process and an essential part of the HL7 V3 development methodology. RIM expresses the data content needed in a specific clinical or administrative context and provides an explicit representation of the semantic and lexical connections that exist between the information carried in the fields of HL7 messages. The RIM is essential to increasing precision and reducing implementation costs. Models are available.

HL7 Development Framework - ISO/HL7 27931
The HL7 Version 3 Development Framework (HDF) is a continuously evolving process that seeks to develop specifications that facilitate interoperability between healthcare systems. The HL7 RIM, vocabulary specifications, and model-driven process of analysis and design combine to make HL7 Version 3 one methodology for development of consensus-based standards for healthcare information system interoperability. The HDF is the most current rendition of the HL7 V3 development methodology.
The HDF documents the processes, tools, actors, rules, and artifacts relevant to development of all HL7 standard specifications, not just messaging. Eventually, the HDF will encompass all of the HL7 standard specifications, including any new standards resulting from analysis of electronic health record architectures and requirements.

HL7 specifications draw upon codes and vocabularies from a variety of sources. The V3 vocabulary work assures that the systems implementing HL7 specifications have an unambiguous understanding of the code sources and code value domains they are using.

V3 Messaging
The HL7 version 3 messaging standard defines a series of electronic messages (called interactions) to support any and all healthcare workflows. HL7 v3 messages are based on an XML encoding syntax.
V3 Clinical Document Architecture - ISO 10781
The HL7 version 3 Clinical Document Architecture (CDA) is an XML-based markup standard intended to specify the encoding, structure and semantics of clinical documents for exchange.



Methods applied by HL7

Arden syntax
The Arden syntax is a language for encoding medical knowledge. HL7 adopted and oversees the standard beginning with Arden syntax 2.0. These Medical Logic Modules (MLMs) are used in the clinical setting as they can contain sufficient knowledge to make single medical decisions. They can produce alerts, diagnoses, interpretations, and contain a quality assurance function and administrative support. An MLM must run on a computer that meets the minimum system requirements and has the correct program installed. Then, the MLM can give advice for when and where it is needed.

A large portion of HL7 messaging is transported by Minimal Lower Layer Protocol (MLLP).

CCOW, or "Clinical Context Object Workgroup," is a standard protocol designed to enable disparate applications to synchronize in real-time, and at the user-interface level.

Functional EHR and PHR specifications
Functional specifications for an electronic health record.

Country specific aspects

The German chapter of HL7 was founded in 1993. This is an entity for benefit to the public and registered as an association as HL7 e. V.
Due to federal structure of operational administration in German healthcare, the standardization aspect is much behind the possibilities of the public economy and due to competitive interests in industry of low normative impact to healthcare information systems development. Currently HL7 in Germany still operates as an informal cluster without direct affiliation to national standardization.
The voluntary membership in HL7 relies on personal interest and engagement of clinical users and mainly on industrial interest: Clinical memberships are in minority. There is no membership of governmental administration and thus low contribution to ongoing discussion e.g. on patient data records (EPA = elektronische Patientenakte) balancing data availability vs. data security. Impact on productivity for clininal information systems (KIS = Krankenhaus-Informationssysteme) is of no importance yet, as the variability of KIS has not been challenged by HL7.
Governmental funding for a broader adoption of HL7 does yet not exist in Germany, neither on federal level nor in most of the regional governments.

Laika The Certification Commission for Healthcare Information Technology (CCHIT) has developed an open-source program called Laika to test EHR software for compliance with CCHIT interoperability standards.


HL7’s initial involvement in the Health Insurance Portability and Accountability Act (HIPAA) legislation began in 1996 with the formation of the Attachments special interest group to standardize the supplemental information needed to support health care insurance, and other e-commerce transactions. The initial deliverable of this group was six recommended Claims Attachments for the Notice of Proposed Rule Making (NPRM) process. Future attachment projects include, but are not limited to, Home Health, Skilled Nursing Facility, durable medical equipment (DME), end stage renal disease (ESRD), and Pre-Authorization and Referrals. The Attachment special interest group is responsible for implementing the Administrative Simplification provisions of HIPAA mandates, providing on-going support, and representing HL7 in the HIPAA Designated Standards Maintenance Organization (DSMO)efforts. Its purpose is to encourage the use of HL7 for uniform implementation of this supplemental information. This SIG coordinates industry input to produce and maintain guides for HL7 messages that can stand alone or be embedded within ANSI_X12 transactions.

Hurricane Katrina
The HL7 group joined forces with the Electronic Health Record Vendors Association (EHRVA) to assist patients in the aftermath of Hurricane Katrina. Members of both organizations were actively working on activities with local, state wide and national agencies (including the DHHS and the CDC) to provide solutions for those in the affected area.