Health Level-7 or HL7 refers to a set of international standards for transfer of clinical and administrative
data between Hospital information systems.
These standards focus on the application layer, which is "layer 7" in the OSI model.
The HL7 standards are produced by the Health Level Seven International, an international
standards organization, and are adopted by other standards issuing bodies such as American
National Standards Institute and International Organization for Standardization.
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 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, document standards, application standards, and messaging
standards.
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.
The Reference Information Model and the HL7 Development Framework are the basis of the
HL7 Version 3 standards development process.
RIM is the representation of the HL7 clinical data and the life cycle of messages or groups
of messages.
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.
HL7 standards: 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 Clinical Context Object Workgroup – an interoperability
specification for the visual integration of user applications
Claims Attachments – a Standard Healthcare Attachment to augment another healthcare transaction
Clinical Document Architecture – an exchange model for clinical documents, based on HL7
Version 3 Electronic Health Record / Personal Health
Record – in support of these records, a standardized description of health and medical
functions sought for or available Structured Product Labeling – 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.
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.
HL7 v2.x messages use a human-readable, non-XML encoding syntax based on segments and one-character
delimiters.
Segments have composites 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 default delimiters are vertical bar or pipe for the field separator, caret for the
component separator, and ampersand for the subcomponent separator.
The tilde is the default repetition separator.
Each segment starts with a 3-character string which 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 record.
MSH is the header record, PID the Patient Identity, PV1 is the Patient Visit information,
etc.
The 5th field in the PID record is the patient's name, in the order, family name, given name,
second names, and suffix.
Depending on the HL7 standard version, more fields are available in the field for adding
additional patient name information.
MSH|^~\&|MegaReg|XYZHospC|SuperOE|XYZImgCtr|20060529090131-0500||ADT^A01^ADT_A01|01052901|P|2.5 EVN||200605290901||||200605290900
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
HL7 v2.x has allowed for the interoperability between electronic Patient Administration
Systems, Electronic Practice Management systems, Laboratory Information Systems, Dietary, Pharmacy
and Billing systems as well as Electronic Medical Record or Electronic Health Record
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 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 and object-oriented
principles.
RIM - ISO/HL7 21731 The Reference Information Model 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 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 Secure Text messages to support all healthcare workflows.
HL7 v3 messages are based on an XML encoding syntax, as shown in this example:
Clinical Document Architecture - ISO/HL7 27932 The HL7 Clinical Document Architecture 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 provides consistency between all
HL7 artifacts, and enables a standardized approach to Enterprise Architecture 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 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, also known as Lower Layer Protocol.
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 is a variation of MLLP that includes a checksum to help verify
message integrity.
Amongst other software vendors, MLLP is supported by Microsoft and Oracle.
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.
Functional EHR and PHR specifications Functional specifications for an electronic
health record.
See also Clinical Document Architecture
CDISC DICOM
Electronic medical record eHealth
EHRcom European Institute for Health Records
FHIR Gello Expression Language
Health Informatics Health Informatics Service Architecture
Healthcare Services Specification Project HL7 SAIF
Integrating the Healthcare Enterprise(IHE) ISO TC 215
LOINC Mirth
openEHR Foundation Public Health Information Network
SNOMED, SNOMED CT References
This article incorporates text from an open source work, under the Creative Commons Attribution-ShareAlike
3.0 license: Spronk 2007.
External links HL7.org site
What does HL7 enablement means?
HL7 is a member of the Joint Initiative on SDO Global Health Informatics Standardization
HL7 Tools Page Australian Healthcare Messaging Laboratory
- Online HL7 Message Testing and Certification Comprehensive Implementation of HL7 v3 Specifications
in Java NIST HL7 Conformance Testing Framework
ICH-HL7 Regulated Product Submissions Critical reviews
HL7 RIM: An Incoherent Standard HL7 RIM Under Scrutiny
HL7 WATCH Update 2013: Human Action in the Healthcare
Domain: A Critical Analysis of HL7’s Reference Information Model