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Health Level Seven, abbreviated to HL7, is a range of global standards for the transfer of clinical and administrative health data between applications with the aim to improve patient outcomes and health system performance. The HL7 standards focus on the application layer, which is "layer 7" in the
Open Systems Interconnection model The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems inter ...
. The standards are produced by
Health Level Seven International Health Level Seven International (HL7) is a Nonprofit organization, non-profit ANSI-accredited standards development organization that develops standards that provide for global health data interoperability. The 2.x versions of the standards a ...
, 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 The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...
and
International Organization for Standardization The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. M ...
. There are a range of primary standards that are commonly used across the industry, as well as secondary standards which are less frequently adopted.


Purpose

Health organizations typically have many different computer systems used to process different patient administration or clinical tasks, such as billing, medication management, patient tracking, and documentation. All of these systems should communicate, or "interface", with each other when they receive new information or when they wish to retrieve information. HL7 International specifies a number of flexible standards, guidelines, and methodologies by which these healthcare systems can communicate with each other. The standards allow for easier 'interoperability' of healthcare data as it is shared and processed uniformly and consistently by the different systems. This allows clinical and non-clinical data to be shared more easily, theoretically improving patient care and health system performance.


Primary standards

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 (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 Structured Product Labeling (SPL) is a Health Level Seven International (HL7) standard which defines the content of human prescription drug labeling in an XML format. The "drug labeling" includes all published material accompanying a drug, such ...
(SPL) – the published information that accompanies a medicine, based on HL7 Version 3 * Clinical Context Object Workgroup (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, , like ''fire'') standard is a set of rules and specifications for the secure exchange of electronic health care data. It is designed to be flexible and adaptable, so that it can be used in a ...
(FHIR) – a standard for the exchange of resources *
Arden Syntax Arden syntax is a markup language designed for representing and sharing medical knowledge in a standardized, executable format. It is primarily used by clinical decision support systems to generate alerts, interpretations, and manage information ...
– a grammar for representing medical conditions and recommendations as a Medical Logic Module (MLM) * Claims Attachments – a Standard Healthcare Attachment to augment another healthcare transaction * Functional Specification of
Electronic Health Record An electronic health record (EHR) is the systematized collection of electronically stored patient and population health information in a digital format. These records can be shared across different health care settings. Records are shared thro ...
(EHR) and
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 (EMR), which is oper ...
(PHR) systems – a standardized description of health and medical functions sought for or available in such software applications *
GELLO Gello (), 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. Women believed to be und ...
– a standard expression language used for clinical decision support


HL7 Version 2

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 more than ten iterations. The v2.x standards are
backward compatible In telecommunications and computing, backward compatibility (or backwards compatibility) is a property of an operating system, software, real-world product, or technology that allows for interoperability with an older legacy system, or with inpu ...
, meaning 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 data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...
encoding syntax based on segments ( lines) and one-character
delimiter A delimiter is a sequence of one or more Character (computing), characters for specifying the boundary between separate, independent regions in plain text, Expression (mathematics), mathematical expressions or other Data stream, data streams. An ...
s. 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 de ...
between the plethora of digital health systems, from Patient Administration Systems, to Electronic Health Records, and specialised Laboratory and Radiology Information Systems. Currently, the HL7 v2.x messaging standard is supported by every major health informatics vendor in the United States.


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 Semantics is the study of linguistic Meaning (philosophy), meaning. It examines what meaning is, how words get their meaning, and how the meaning of a complex expression depends on its parts. Part of this process involves the distinction betwee ...
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 * Lexical ...
connections that exist between the information carried in the fields of HL7 messages. HL7 Development Framework -
ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...
/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 the development of consensus-based standards for healthcare information systems
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 de ...
. 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 the development of all HL7 standard specifications. Eventually, the HDF will encompass all of the HL7 standard specifications, including any new standards resulting from the 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

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. The standard was jointly published with ISO as ISO/HL7 27932.


Continuity of Care Document

The Continuity of Care Document framework is a US-specific standard for the exchange of medical summaries, based on the Clinical Document Architecture standard.


Structured Product Labeling

Structured Product Labeling describes the published information that accompanies a medicine, based on HL7 Version 3.


Clinical Context Object Workgroup

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.


Other standards and methods


Fast Healthcare Interoperability Resources (FHIR)

Fast Healthcare Interoperability Resources is a modern interoperability specification from HL7 International designed to be easier to implement, more open, and more extensible than HL7 versions 2.x or 3.x. It leverages a modern web-based suite of API technology, including a
HTTP HTTP (Hypertext Transfer Protocol) 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 Web, wher ...
-based
RESTful REST (Representational State Transfer) is a software architectural style that was created to describe the design and guide the development of the architecture for the World Wide Web. REST defines a set of constraints for how the architecture of ...
protocol,
HTML Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheets ( ...
and Cascading Style Sheets for user interface integration, a choice of
JSON JSON (JavaScript Object Notation, pronounced or ) is an open standard file format and electronic data interchange, data interchange format that uses Human-readable medium and data, human-readable text to store and transmit data objects consi ...
or
XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...
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. Th ...
for authorization and
Atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
for query results. The main purpose of the FHIR standard is to ensure interoperability between different computer systems. It defines the data format and protocol for exchanging medical information, regardless of how it is stored in these systems.


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 service 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 designed for representing and sharing medical knowledge in a standardized, executable format. It is primarily used by clinical decision support systems to generate alerts, interpretations, and manage information ...
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.


Clinical Quality Language

Clinical Quality Language (CQL) is a
ANSI The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...
certified clinically focused high-level expression language standard curated by Health Level 7. It is designated for clinical knowledge sharing in the domains of electronic clinical quality measurement and clinical decision support. Clinical quality language is being used for a variety of clinical applications including
WHO The World Health Organization (WHO) is a specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Geneva, Switzerland, and has 6 regional offices and 15 ...
SMART guidelines where it is used for encoding decision logic and performance indicators. The
Centers for Medicare & Medicaid Services The Centers for Medicare & Medicaid Services (CMS) is a federal agency within the United States Department of Health and Human Services (HHS) that administers the Medicare program and works in partnership with state governments to administer M ...
adopted CQL for clinical quality measure specifications since 2019. CQL allows modular and flexible expression of logic and is both human-readable and machine processable.Measures management system
cms.gov Retrieved 3 April 2024
An implementation of CQL was
open sourced Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. Open ...
and published by the
National Committee for Quality Assurance The National Committee for Quality Assurance (NCQA) is an independent 501(c)(3) nonprofit organization A nonprofit organization (NPO), also known as a nonbusiness entity, nonprofit institution, not-for-profit organization, or simply a non ...
in 2023 with the aim of encouraging adoption of the language.


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. 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, such as the Internet. The protocol is widely used in applications such as email, instant messaging, and voice over ...
(TLS) or IPsec for safeguarding
Protected health information Protected health information (PHI) under Law of the United States, U.S. law is any information about health status, provision of health care, or payment for health care that is created or collected by a Covered Entity (or a Business Associate of a ...
outside of a secure network.


Functional EHR and PHR specifications

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


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.


See also

* CDISC *
DICOM Digital Imaging and Communications in Medicine (DICOM) is a technical standard for the digital storage and Medical image sharing, transmission of medical images and related information. It includes a file format definition, which specifies the str ...
* DVTk *
Electronic medical record An electronic health record (EHR) is the systematized collection of electronically stored patient and population health information in a digital format. These records can be shared across different health care settings. Records are shared thro ...
*
eHealth eHealth describes healthcare services which are supported by digital processes, communication or technology such as electronic prescribing, Telehealth, or Electronic Health Records (EHRs). The term "eHealth" originated in the 1990s, initially c ...
*
EHRcom The Health informatics - Electronic Health Record Communication (EN 13606) was the European Standard for an information architecture to communicate patients' electronic health records (EHRs). The standard was later adopted as ISO 13606 and later ...
*
European Institute for Health Records The European Institute for Health Records or EuroRec Institute is a non-profit organization founded in 2002 as part of the ProRec initiative. On 13 May 2003, the institute was established as a non-profit organization under French law. Current Pre ...
(
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
) *
Fast Healthcare Interoperability Resources The Fast Healthcare Interoperability Resources (FHIR, , like ''fire'') standard is a set of rules and specifications for the secure exchange of electronic health care data. It is designed to be flexible and adaptable, so that it can be used in a ...
*
Health Informatics Health informatics combines communications, information technology (IT), and health care to enhance patient care and is at the forefront of the medical technological revolution. It can be viewed as a branch of engineering and applied science. ...
*
Health Informatics Service Architecture The European Committee for Standardization ( CEN) Standard Architecture for Healthcare Information Systems (ENV 12967), Health Informatics Service Architecture or HISA is a standard that provides guidance on the development of modular open informat ...
(HISA) * Integrating the Healthcare Enterprise(IHE) *
ISO TC 215 The ISO/TC 215 is the International Organization for Standardization's (ISO) Technical Committee (TC) on health informatics. TC 215 works on the standardization of Health Information and Communications Technology (ICT), to allow for compatibility ...
*
LOINC Logical Observation Identifiers Names and Codes (LOINC) is a database and universal standard for identifying medical laboratory observations. First developed in 1994, it was created and is maintained by the Regenstrief Institute, a US nonprofit m ...
* NextGen Connect *
Public Health Information Network The Public Health Information Network (PHIN) is a US national initiative, developed by the Centers for Disease Control and Prevention (CDC), for advancing fully capable and interoperable information systems in public health organizations. The ini ...
*
SNOMED The Systematized Nomenclature of Medicine (SNOMED) is a systematic, computer-processable collection of medical terms, in human and veterinary medicine, to provide codes, terms, synonyms and definitions which cover anatomy, diseases, findings, pr ...
and
SNOMED CT SNOMED CT or SNOMED Clinical Terms is a systematically organized computer-processable collection of medical terms providing codes, terms, synonyms and definitions used in clinical documentation and reporting. SNOMED CT is considered to be the mo ...


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 Agent-based software American National Standards Institute standards Standards for electronic health records Data coding framework Health informatics