Health Level 7

Health Level 7

Health Level Seven (HL7), is an all-volunteer, non-profit organization involved in development of international healthcare informatics interoperability standards.[1] "HL7" is also used to refer to some of the specific standards created by the organization (e.g., HL7 v2.x, v3.0, HL7 RIM).[2]

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.[citation needed]



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.[3]

HL7 promotes the use of such informatics standards within and among healthcare organizations to increase the effectiveness and efficiency of healthcare information delivery for the benefit of all.[citation needed]

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.[4]
  • 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.[citation needed]

The organizational structure of HL7 Inc. is as follows:[citation needed]

  • 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).[5]

HL7 is one of several American National Standards Institute 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 United States. 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 layer of the ISO OSI Reference model also known as the application layer. 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.[1]


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.[citation needed]

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.[6]

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.[citation needed]

HL7 develops conceptual standards (e.g., HL7 RIM), document standards (e.g., HL7 CDA), application standards (e.g., HL7 CCOW), and messaging standards (e.g., 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.[7]

HL7 encompasses the complete life cycle of a standards specification including the development, adoption, market recognition, utilization, and adherence.[citation needed] Business use of the HL7 standards requires a paid organizational membership in HL7, Inc. HL7 Members can access standards for free, and non-members can buy the standards from HL7 or ANSI.

The Reference Information Model (RIM) and the HL7 Development Framework (HDF) are the basis of the HL7 Version 3 standards development process. RIM is the representation of the HL7 clinical data (domains) and the life cycle of messages or groups of messages.[8] HDF is a project to specify the processes and methodology used by all the HL7 committees for project initiation, requirements analysis, standard design, implementation, standard approval process, etc.[9]

HL7 standards:[10]

  • Version 2.x Messaging Standard – an interoperability specification for health and medical transactions
  • Version 3 Messaging Standard – an interoperability specification for health and medical transactions, based on RIM
  • Version 3 Rules/GELLO – a standard expression language used for clinical decision support
  • Arden Syntax – a grammar for representing medical conditions and recommendations as a Medical Logic Module (MLM)
  • Clinical Context Object Workgroup (CCOW) – an interoperability specification for the visual integration of user applications
  • Claims Attachments – a Standard Healthcare Attachment to augment another healthcare transaction
  • Clinical Document Architecture (CDA) – an exchange model for clinical documents, based on HL7 Version 3
  • Electronic Health Record (EHR) / Personal Health Record (PHR) – in support of these records, a standardized description of health and medical functions sought for or available
  • Structured Product Labeling (SPL) – the published information that accompanies a medicine, based on HL7 Version 3

HL7 version 2.x

The HL7 version 2 standard has the aim to support hospital workflows. It was originally created in 1989.[11]

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. The v2.x standards are backward compatible (i.e. a message based on version 2.3 will be understood by an application that supports version 2.6).

HL7 v2.x messages use a human-readable (ASCII), non-XML encoding syntax based on segments (lines) and one-character delimiters.[12] Segments have composites (fields) separated by the composite delimiter. A composite can have sub-composites separated by the sub-composite delimiter, and sub-composites can have sub-sub-composites separated by the sub-sub-composite delimiter. The first field (composite) in each segment contains the 3-character segment name. Each segment of the message contains one specific category of information. Every message has MSH as its first segment, which includes a field that identifies the message type. The message type determines the expected segment names in the message.[13] The segment names for a particular message type are specified by the segment grammar notation used in the HL7 standards.

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.[14]

HL7 version 3

The HL7 version 3 standard has the aim to support 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 increase precision and reduce 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 edition of the HL7 V3 development methodology.

The HDF not only documents messaging, but also the processes, tools, actors, rules, and artifacts relevant to development of all HL7 standard specifications. 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 ensures 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 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

Services Aware Interoperability Framework

The HL7 Services-Aware Enterprise Architecture Framework (SAIF) provides consistency between all HL7 artifacts, and enables a standardized approach to Enterprise Architecture (EA) development and implementation, and a way to measure the consistency.

SAIF is a way of thinking about producing specifications that explicitly describe the governance, conformance, compliance, and behavioral semantics that are needed to achieve computable semantic working interoperability. The intended information transmission technology might use a messaging, document exchange, or services approach.

SAIF is the framework that is required to rationalize interoperability of other standards. SAIF is an architecture for achieving interoperability, but it is not a whole-solution design for enterprise architecture management.

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.[citation needed] They can produce alerts, diagnoses, and interpretations along with 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), also known as Lower Layer Protocol (LLP).[15] For transmitting via TCP/IP, header and trailer characters are added to the message to identify the beginning and ending of the message because TCP/IP is a continuous stream of bytes. Hybrid Lower Layer Protocol (HLLP) is a variation of MLLP that includes a checksum to help verify message integrity. Amongst other software vendors, MLLP is supported by Microsoft[16] and Oracle.[17]


CCOW, or "Clinical Context Object Workgroup," is a standard protocol designed to enable disparate applications to share user context and patient context in real-time, and at the user-interface level. CCOW implementations typically require a CCOW vault system to manage user security between applications.

Functional EHR and PHR specifications

Functional specifications for an electronic health record.

Country specific aspects


HL7 Australia was established in 1998.

Australia was an early adopter of the HL7 V2.x standards, which are now ubiquitously used in Australian public and private healthcare organisations.

The localisation of the HL7 standards is undertaken in cooperation with the national standards body, Standards Australia.

HL7 Australia closely cooperates with the National E-Health Transition Authority (NEHTA).


National IT services for healthcare

The Social Insurance Institution of Finland is building a national ePrescribing and patient record archival service based on HL7 CDA R2 and V3 messages. Phased deployment is scheduled for 2008-2011. Version 2 messaging is widely deployed in most hospitals and healthcare centers. CDA R1 is used in sharing patient records on a regional level.


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 operates as an informal cluster and collaborates with the national standardization body.[18]

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 low 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 hospital information systems (called KIS = Krankenhaus-Informationssysteme in German) is of no importance yet, as the variability of HIS systems 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.


HL7 Italia was established in 2003 and it is responsible for the localization of this standard in the Italian context. The aim is to stimulate and direct the regional and national contributions towards the standard development and to promote the modernization of Italian health IT. HL7 Italia members are suppliers of health IT market. Some Italian regions, regional In-Houses, Governative Agencies, Public Research Institutes, local Hospital departments and individual IT professionals are HL7 Italia members.

The Netherlands

AORTA - National Healthcare ICT infrastructure

AORTA is the Dutch national infrastructure for the exchange of data between healthcare providers. AORTA uses HL7 version 3 messages and documents as its core mechanism for information exchange. The initial specifications were created in 2003. The Dutch Ministry of Health is working on a virtual national Electronic Patient Records (EPR) which will enable healthcare providers to share patient data. This development takes place in close collaboration with Nictiz, the National Information and Communication Technology Institute for Healthcare. Nictiz coordinates its efforts with regard to the usage of HL7 version 3 with the volunteers of HL7 the Netherlands.

Almost all hospitals use HL7 version 2 to support hospital-internal workflows. EDIfact is being used to support workflows involving general practitioners (GPs/PCPs). EDIfact will be slowly replaced by HL7 version 3.


HLH - Health Life Horizon

HLH (a national project) is being carried out at School of Electrical Engineering and Computer Sciences of National University of Science and Technology and is supported by Government of Pakistan with funds provided by National ICT R&D Fund. HLH basic theme is to target health care information exchange and interoperability using HL7 version 3. Though the penetration and use of HL7 in Pakistan is lower than the countries like US and that of Europe. But its getting popularity among the stakeholders in Pakistan. HLH Team members have been participating in HL7 International Working Group meetings and conferences for last two years. On Oct 1, 2010 HL7 International announced Pakistan Chapter formally at 24th Plenary and WGM in Cambridge USA. Pakistan is now the 37th affiliate of HL7 International around the world. HL7 Pakistan is now officially authorized to give memberships to local organizations along with other privileges like certification, training etc.



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 a set of 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 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.

See also


  1. ^ a b "About Health Level Seven". Health Level Seven. 
  2. ^ "Healthcare Interoperability Glossary". Corepoint Health. 
  3. ^
  4. ^ "Contact Health Level Seven". Health Level Seven. 
  5. ^ ANSI
  6. ^ HL7 Membership Numbers as sent to the HL7 affiliates on 2007-11-08.
  7. ^ "CCDP Project Overview". California HealthCare Foundation. 
  8. ^ "HL7 Reference Information Model". HL7. 
  9. ^ "HL7 Development Framework (HDF)". HL7. 
  10. ^ "HL7 Standards". HL7. 
  11. ^ "HL7 FAQs". HL7. 
  12. ^ "Understanding HL7 Messages". iNTERFACEWARE. 
  13. ^ "HL7 Messages and Descriptions". iNTERFACEWARE. 
  14. ^ "Standards Organizations". Assistant Secretary for Planning and Evaluation (ASPE), Health and Human Services (HHS). 
  15. ^ "LLP - Lower Layer Protocol". iNTERFACEWARE. 
  16. ^ "MLLP Receive and Send Components". MSDN. 
  17. ^ "Oracle Application Server Integration B2B User's Guide, Supported Protocols". Oracle. 
  18. ^ DIN NAMed Jahresbericht 2007

External links

Critical reviews

Open source tools

There are a number of FOSS based tools that can foster worldwide adoption of the HL7 standards

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