Health Level Seven or HL7 refers to a set of international standards for transfer of clinical and administrative data between software applications used by various healthcare providers. These standards focus on the application layer, which is "layer 7" in the

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

. The HL7 standards are produced by

Health Level Seven International Health Level Seven International (HL7) is a non-profit ANSI-accredited standards development organization that develops standards that provide for global health data interoperability. The 2.x versions of the standards are the most commonly use ...

, an international

standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary function is developing, coordinating, promulgating, revising, amending, reissuing, interpr ...

, and are adopted by other standards issuing bodies such as American National Standards Institute and

International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Art ...

. 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, or when they wish to retrieve information, but not all do so. HL7 International 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 International considers the following standards to be its primary standards – those standards that are most commonly used and implemented: * 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 *

Clinical Document Architecture The HL7 Clinical Document Architecture (CDA) is an XML-based markup standard intended to specify the encoding, structure and semantics of clinical documents for exchange. In November 2000, HL7 published Release 1.0. The organization published ...

(CDA) – an exchange model for clinical documents, based on HL7 Version 3 *

Continuity of Care Document The Continuity of Care Document (CCD) specification is an XML-based markup standard intended to specify the encoding, structure, and semantics of a patient summary clinical document for exchange. Structure The CCD specification is a constraint o ...

(CCD) – a US specification for the exchange of medical summaries, based on CDA. * Structured Product Labeling (SPL) – the published information that accompanies a medicine, based on HL7 Version 3 *

Clinical Context Object Workgroup In the context of Health informatics, CCOW (''pr'' /seacow/) or Clinical Context Object Workgroup is a Health Level Seven International standard protocol designed to enable disparate applications to synchronize in real time, and at the user-interfac ...

(CCOW) – an interoperability specification for the visual integration of user applications Other HL7 standards/methodologies include: *

Fast Healthcare Interoperability Resources The Fast Healthcare Interoperability Resources' (FHIR, pronounced "fire") standard is a set of rules and specifications for exchanging electronic health care data. It is designed to be flexible and adaptable, so that it can be used in a wide rang ...

(FHIR) – a standard for the exchange of resources *

Arden Syntax Arden syntax is a markup language used for representing and sharing medical knowledge. This clinical and scientific knowledge language is used in an executable format by clinical decision support systems to generate alerts, interpretations, and ...

– a grammar for representing medical conditions and recommendations as a

Medical Logic Module A medical logic module (MLM) is an independent unit in a healthcare knowledge base that represents the knowledge published on a requirement for treating a patient according to a single medical decision. Possible usage is with an event monitor p ...

(MLM) * Claims Attachments – a Standard Healthcare Attachment to augment another healthcare transaction * Functional Specification of Electronic Health Record (EHR) /

Personal Health Record A personal health record (PHR) is a health record where health data and other information related to the care of a patient is maintained by the patient. This stands in contrast to the more widely used electronic medical record, which is operated ...

(PHR) systems – a standardized description of health and medical functions sought for or available in such software applications *

GELLO Gello ( grc, Γελλώ), in Greek mythology, is a female demon or revenant who threatens the reproductive cycle by causing infertility, miscarriage, and infant mortality. By the Byzantine era, the () were considered a class of beings. Wome ...

– a standard expression language used for clinical decision support

Primary standards

HL7's primary standards are those standards that

considers to be most commonly used and implemented.

Version 2 messaging

The HL7 version 2 standard (also known as Pipehat) has the aim to support hospital workflows. It was originally created in 1989. 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, 2.6, 2.7, 2.7.1, 2.8, 2.8.1 and 2.8.2. The v2.x standards are

backward compatible Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially in ...

(e.g., a message based on version 2.3 will be understood by an application that supports version 2.6). HL7 v2.x messages use a non-

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...

encoding syntax based on segments ( lines) and one-character delimiters. Segments have composites (

field Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grass ...

s) separated by the composite delimiter. A composite can have sub-composites (components) separated by the sub-composite delimiter, and sub-composites can have sub-sub-composites (subcomponents) separated by the sub-sub-composite delimiter. The default delimiters are

carriage return A carriage return, sometimes known as a cartridge return and often shortened to CR, or return, is a control character or mechanism used to reset a device's position to the beginning of a line of text. It is closely associated with the line feed ...

for the segment separator, vertical bar or pipe (, ) for the field separator, caret (^) for the component separator, ampersand (&) for the subcomponent separator, and number sign (#) for the default truncation separator. The tilde (~) is the default repetition separator. Each segment starts with a 3-character string that identifies the segment type. 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 types in the message. The segment types used in a particular message type are specified by the segment grammar notation used in the HL7 standards. The following is an example of an admission message. MSH is the header segment, PID the Patient Identity, PV1 is the Patient Visit information, etc. The 5th field in the PID segment is the patient's name, in the order, family name, given name, second name (or their initials), suffix, etc. Depending on the HL7 V2.x standard version, more fields are available in the segment for additional patient information. HL7 v2.x has allowed for the

interoperability Interoperability is a characteristic of a product or system to work with other products or systems. While the term was initially defined for information technology or systems engineering services to allow for information exchange, a broader defi ...

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 An electronic health record (EHR) is the systematized collection of patient and population electronically stored health information in a digital format. These records can be shared across different health care settings. Records are shared throu ...

(EMR) or Electronic Health Record (EHR) systems. Currently, the HL7 v2.x messaging standard is supported by every major medical information systems vendor in the United States.

Version 3 messaging

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 Lexical may refer to: Linguistics * Lexical corpus or lexis, a complete set of all words in a language * Lexical item, a basic unit of lexicographical classification * Lexicon, the vocabulary of a person, language, or branch of knowledge * Lex ...

connections that exist between the information carried in the fields of HL7 messages. HL7 Development Framework -

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * 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

. 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 Secure Text messages (called ''interactions'') to support all healthcare workflows. HL7 v3 messages are based on an XML encoding syntax, as shown in this example:

Clinical Document Architecture (CDA)

The HL7

(CDA) is an XML-based markup standard intended to specify the encoding, structure and semantics of clinical documents for exchange. The standard was jointly published with ISO as ISO/HL7 27932.

Continuity of Care Document (CCD)

CCD is a US specification for the exchange of medical summaries, based on CDA.

Structured Product Labeling (SPL)

SPL describes the published information that accompanies a medicine, based on HL7 Version 3.

CCOW

CCOW In the context of Health informatics, CCOW (''pr'' /seacow/) or Clinical Context Object Workgroup is a Health Level Seven International standard protocol designed to enable disparate applications to synchronize in real time, and at the user-interfa ...

, 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.

Other standards and methods

Fast Healthcare Interoperability Resources (FHIR)

Fast Healthcare Interoperability Resources is a draft standard from HL7 International designed to be easier to implement, more open and more extensible than version 2.x or version 3. It leverages a modern web-based suite of API technology, including a

HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide We ...

-based RESTful protocol,

HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaSc ...

and Cascading Style Sheets for user interface integration, a choice of JSON or

for data representation,

OAuth OAuth (short for "Open Authorization") is an open standard for access delegation, commonly used as a way for internet users to grant websites or applications access to their information on other websites but without giving them the passwords. T ...

for authorization and

ATOM Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, ...

for query results.

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 Arden syntax is a markup language used for representing and sharing medical knowledge. This clinical and scientific knowledge language is used in an executable format by clinical decision support systems to generate alerts, interpretations, and ...

is a language for encoding medical knowledge. HL7 International 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, 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.

MLLP

A large portion of HL7 messaging is transported by Minimal Lower Layer Protocol (MLLP), also known as Lower Layer Protocol (LLP) or Minimum Layer Protocol (MLP). 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, Oracle,

Cleo Cleo may refer to: Entertainment * ''Cleo'' (magazine), an Australian magazine established in 1972, now active in Indonesia, Malaysia, Singapore, and Thailand * Cleo (group), a South Korean girl group formed in 1999 * ''Cleo'' (play), by Lawren ...

. MLLP contains no inherent security or encryption but relies on lower layer protocols such as

Transport Layer Security Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securi ...

(TLS) or

IPsec In computing, Internet Protocol Security (IPsec) is a secure network protocol suite that authenticates and encrypts packets of data to provide secure encrypted communication between two computers over an Internet Protocol network. It is used in ...

for safeguarding Protected health information outside of a secure network.

Functional EHR and PHR specifications

Functional specifications for an electronic health record.

Message details

The OBR segment

An OBR Segment carries information about an exam, diagnostic study/observation. It is a required segment in an ORM (order message) or an ORU (Observation Result) message.

References

External links

HL7.org site

What does HL7 education mean?
* HL7 International is a member of th
Joint Initiative on SDO Global Health Informatics Standardization

Australian Healthcare Messaging Laboratory (AHML) - Online HL7 Message Testing and Certification

Comprehensive Implementation of HL7 v3 Specifications in Java

NIST HL7 Conformance Testing Framework

ICH-HL7 Regulated Product Submissions

HL7 Programming Tutorials
Short Tutorials on many HL7 concepts for Programmers.

Critical reviews

HL7 RIM: An Incoherent Standard

HL7 RIM Under Scrutiny
(attempted rebuttal)(publication date?)
HL7 WATCH
* Update 2013
Human Action in the Healthcare Domain: A Critical Analysis of HL7’s Reference Information Model
{{health software International standards Multi-agent systems American National Standards Institute standards Standards for electronic health records Data coding framework