Editing Health Level 7 (section)

== Primary standards ==
[[Health Level Seven International|HL7 International]] considers the following standards to be its primary standards – those standards that are most commonly used and implemented:<ref name="HL7 Primary Standards">{{cite web|title=HL7 Primary Standards|url=http://www.hl7.org/implement/standards/product_section.cfm?section=1|publisher=[[Health Level Seven International]]}}</ref>
* 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]] (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]] (CCOW) – an interoperability specification for the visual integration of user applications

Other HL7 standards/methodologies include:<ref>{{cite web|title=HL7 Standards|url=http://www.hl7.org/implement/standards/index.cfm?ref=nav|publisher=[[Health Level Seven International]]}}</ref>
* [[Fast Healthcare Interoperability Resources]] (FHIR) – a standard for the exchange of resources  
* [[Arden Syntax]] – a grammar for representing medical conditions and recommendations as a [[Medical logic module|Medical Logic Module]] (MLM)
* Claims Attachments – a Standard Healthcare Attachment to augment another healthcare transaction
* Functional Specification of [[Electronic Health Record]] (EHR) and [[Personal health record|Personal Health Record]] (PHR) systems – a standardized description of health and medical functions sought for or available in such software applications
* [[Gello Expression Language|GELLO]] – a standard expression language used for clinical decision support

===HL7 Version 2===
{{Technical|date=April 2024|section}}
The HL7 version 2 standard (also known as Pipehat) has the aim to support hospital workflows. It was originally created in 1989.<ref>{{cite web|title=HL7 FAQs|url=http://www.hl7.org/about/FAQs/index.cfm?ref=nav|publisher=[[HL7]]}}</ref>

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 compatibility|backward compatible]], 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]] encoding syntax based on segments ([[Line (text file)|line]]s) and one-character [[delimiter]]s.<ref>{{cite web|title=Understanding HL7 Messages|url=http://www.interfaceware.com/understanding_hl7_messages.html|publisher=iNTERFACEWARE}}</ref> Segments have composites ([[Field (computer science)|field]]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]] for the segment separator, vertical bar or pipe (<code>|</code>) for the field separator, caret (<code>^</code>) for the component separator, ampersand (<code>&</code>) for the subcomponent separator, and number sign (#) for the default truncation separator. The tilde (<code>~</code>) 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 <code>MSH</code> as its first segment, which includes a field that identifies the message type. The message type determines the expected segment types in the message.<ref>{{cite web|title=HL7 Messages and Descriptions|url=http://healthstandards.com/blog/2007/09/24/hl7-separator-characters/|publisher=Health Standards}}</ref> 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.  <code>MSH</code> is the header segment, <code>PID</code> the Patient Identity, <code>PV1</code> is the Patient Visit information, etc. The 5th field in the <code>PID</code> 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.

{{pre|
<nowiki>MSH|^~\&|MegaReg|XYZHospC|SuperOE|XYZImgCtr|20060529090131-0500||ADT^A01^ADT_A01|01052901|P|2.5
EVN||200605290901||||
PID|||56782445^^^UAReg^PI||KLEINSAMPLE^BARRY^Q^JR||19620910|M||2028-9^^HL70005^RA99113^^XYZ|260 GOODWIN CREST DRIVE^^BIRMINGHAM^AL^35209^^M~NICKELL’S PICKLES^10000 W 100TH AVE^BIRMINGHAM^AL^35200^^O|||||||0105I30001^^^99DEF^AN
PV1||I|W^389^1^UABH^^^^3||||12345^MORGAN^REX^J^^^MD^0010^UAMC^L||67890^GRAINGER^LUCY^X^^^MD^0010^UAMC^L|MED|||||A0||13579^POTTER^SHERMAN^T^^^MD^0010^UAMC^L|||||||||||||||||||||||||||200605290900
OBX|1|NM|^Body Height||1.80|m^Meter^ISO+|||||F
OBX|2|NM|^Body Weight||79|kg^Kilogram^ISO+|||||F
AL1|1||^ASPIRIN
DG1|1||786.50^CHEST PAIN, UNSPECIFIED^I9|||A</nowiki>
}}

HL7 v2.x has allowed for the [[interoperability]] 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.<ref>{{cite web|title=Standards Organizations|url=http://aspe.hhs.gov/sp/nhii/standards.html|publisher=Assistant Secretary for Planning and Evaluation (ASPE), [[Health and Human Services]] (HHS)}}</ref>

===HL7 Version 3===
The HL7 version 3 standard has the aim to support all healthcare workflows.<ref name="V3">{{cite web|title=HL7 V3 Standard - A High Level Overview|date=26 May 2020|url=https://saravanansubramanian.com/hl7V3intro/}}</ref> 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<ref name="RIM">{{cite web|title=HL7 Reference Information Model|url=http://www.hl7.org/implement/standards/rim.cfm|publisher=[[HL7]]}}</ref> (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 [[lexicon|lexical]] connections that exist between the information carried in the fields of HL7 messages.<ref>{{cite web|title=Tools & Resources – V3 Modeling & Methodology Tools|url=http://www.hl7.org/participate/toolsandresources.cfm|publisher=[[HL7]]}}</ref>

'''HL7 Development Framework - [[International Organization for Standardization|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 the development of consensus-based standards for healthcare information systems [[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 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:<ref>{{cite web|editor-last=Spronk|editor-first=René|title=HL7 Message examples: version 2 and version 3|url=http://www.ringholm.de/docs/04300_en.htm|work=Ringholm|publisher=Ringholm bv|date=16 November 2007}}</ref>{{rp|2.2.1}}

<!--Sample code from Spronk 2007, CC BY-SA 3.0-->
<syntaxhighlight lang="xml"><POLB_IN224200 ITSVersion="XML_1.0" xmlns="urn:hl7-org:v3"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">  
  <id root="2.16.840.1.113883.19.1122.7" extension="CNTRL-3456"/>
  <creationTime value="200202150930-0400"/>
  <!-- The version of the datatypes/RIM/vocabulary used is that of May 2006 -->
  <versionCode code="2006-05"/>
  <!-- interaction id= Observation Event Complete, w/o Receiver Responsibilities -->
  <interactionId root="2.16.840.1.113883.1.6" extension="POLB_IN224200"/>
  <processingCode code="P"/>
  <processingModeCode nullFlavor="OTH"/>
  <acceptAckCode code="ER"/>
  <receiver typeCode="RCV">
    <device classCode="DEV" determinerCode="INSTANCE">
      <id extension="GHH LAB" root="2.16.840.1.113883.19.1122.1"/>
      <asLocatedEntity classCode="LOCE">
        <location classCode="PLC" determinerCode="INSTANCE">
          <id root="2.16.840.1.113883.19.1122.2" extension="ELAB-3"/>
        </location>
      </asLocatedEntity>
    </device>
  </receiver>
  <sender typeCode="SND">
    <device classCode="DEV" determinerCode="INSTANCE">
      <id root="2.16.840.1.113883.19.1122.1" extension="GHH OE"/>
      <asLocatedEntity classCode="LOCE">
        <location classCode="PLC" determinerCode="INSTANCE">
          <id root="2.16.840.1.113883.19.1122.2" extension="BLDG24"/>
        </location>
      </asLocatedEntity>
    </device>
  </sender>
  <!-- Trigger Event Control Act & Domain Content -->
</POLB_IN224200></syntaxhighlight>

===Clinical Document Architecture===
{{main|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.<ref>{{cite book|title=The CDA Book|isbn = 9780857293367|url=https://books.google.com/books?id=rwa6DDB4jY8C|last1 = Boone|first1 = Keith W.|date = 20 May 2011| publisher=Springer }}</ref> The standard was jointly published with ISO as ISO/HL7 27932.

===Continuity of Care Document===
{{main|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===
{{main|Structured Product Labeling}}

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

===Clinical Context Object Workgroup===
{{main|CCOW}}
[[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.