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Areas of Current Investigation |  Implementation Notes |  Selected Resources |  Background

Areas of Current Investigation

In September 2006, HL7 achieved acceptance on the international stage when it became a partner of the International Organization of Standardization (ISO). As part of the ISO, HL7 can "share its products with the International Standards community, thus reducing the need for duplicative work." The organization published HL7 Version 3-Reference Information Model (RIM), representing an early attempt to streamline global standards development. [HL7 Press Release (PDF, 34 KB)]

In December 2005, HL7 and the National Council for Prescription Drug Programs (NCPDP) completed the first phase of a project to streamline electronic prescribing (e-prescribing) messaging capabilities between prescribers and pharmacies and payers. The two groups completed a mapping guidance document to help implementers create e-prescribing messages "for new prescriptions, changes to prescriptions, refills (renewals), cancellation of a prescription, compliance notification, and the sharing of medication history information." [HL7 Press Release (PDF, 42 KB )] The document is available from either HL7 or NCPDP, but only members of these organizations can currently download the document.

On September 23, 2005, HHS Secretary Mike Leavitt proposed the adoption of standards for certain attachments to electronic health care claims, a requirement of the Health Insurance Portability and Accountability Act of 1996 (HIPAA). The proposed standards, published in the Federal Register (Vol. 70, No. 184), apply to electronic transactions that request and provide clinical information for certain types of services billed by the provider to the health plan. The proposal includes the use of the HL7 messaging standard to transmit data.

The National Health Information Network (NHIN) project funded by the Office of the National Coordinator for Health IT (ONCHIT) is using the HL7 v3 protocol heavily within its specifications. Specifically, the HL7 v3 concept of a CCD (Continuity of Care Document) is used to deliver clinical abstracts of patient data between NHIN nodes on the network. When a request is made to a particular node from the NHIN, the data are returned to the NHIN in the format of a CCD. The CCD contains information pertaining to many aspects of patient care, including demographics, lab results, medications, visit histories, vital signs, provider information, and so on.

Implementation Notes

HL7 allows for a high degree of customization. This means that although two products claim they "support HL7," they may not be able to exchange information without a custom interface engine. To connect multiple internal systems (developed by different vendors) using HL7 messages, an interface engine may be necessary. When exchanging data with other institutions, an interface engine is almost always necessary.

The Regenstrief Institute has developed a tool called HL7 Lint that examines HL7 messages for structural and syntactical errors. This tool is useful for testing messages coming across an HL7 message stream as well as for applications that send or receive HL7 messages. The tool is available for free at the organization's LOINC Web Site.

There is great interest in using and parsing CCD files. The CCD files are XML-based documents that contain abstracts of clinical information for a patient. The CCD schema and specification may be obtained from the HL7 Web site. There are several open-source efforts for parsing CCDs including the XML to CSV Spreadsheet Convertor, which converts CCD documents into CSV files using a Microsoft Excel macro.

Selected Resources

LOINC, a Universal Standard for Identifying Laboratory Observations: a 5-year Update
Author(s): McDonald CJ, Huff SM, Suico JG, Hill G, Leavelle D, Aller R, Forrey A, Mercer K, DeMoor G, Hook J, Williams W, Case J, Maloney P
Source: Clin Chem 2003 Apr;49(4):624-33.
Summary: The Logical Observation Identifier Names and Codes (LOINC) database provides a universal code system for reporting laboratory and other clinical observations. It identifies observations in electronic messages such as Health Level Seven (HL7) observation messages. In this way, when hospitals, health maintenance organizations, pharmaceutical manufacturers, researchers, and public health departments receive such messages from multiple sources, they can file the results automatically in the right slots of their medical records, research, and/or public health systems. For each observation, the database includes a code (of which 25,000 are laboratory test observations), a long formal name, a "short" 30-character name, and synonyms. LOINC codes are used by large reference laboratories and Federal agencies and are part of the Health Insurance Portability and Accountability Act (HIPAA) attachment proposal. Laboratories should include LOINC codes in their outbound HL7 messages so that clinical and research clients can integrate these results easily into their clinical and research repositories.

The HL7 Clinical Document Architecture
Author(s): Dolin RH, Alschuler L, Beebe C, Biron PV, Boyer SL, Essin D, Kimber E, Lincoln T, Mattison JE
Source: J Am Med Inform Assoc (JAMIA) 2001 Nov-Dec;8(6):552-69.
Summary: Health Level 7 (HL7) is developing standards for the representation of clinical documents (such as discharge summaries and progress notes). These document standards make up the HL7 Clinical Document Architecture (CDA). This article presents the approach and objectives of the CDA, along with a technical overview of the standard. The CDA is a document markup standard that specifies the structure and semantics of clinical documents and can include text, images, sounds, and other multimedia content. The first release of the standard has attempted to fill an important gap by addressing common and largely narrative clinical notes. As part of the emerging HL7 version 3 family of standards, the CDA derives its semantic content from the shared HL7 Reference Information Model and is implemented in Extensible Markup Language (XML). The HL7 mission is to develop standards that enable semantic interoperability across all platforms; the CDA is helping to achieve this vision.


Health Level Seven (HL7), an American National Standards Institute (ANSI) accredited Standards Developing Organization (SDO), is responsible for the continued development and maintenance of the HL7 clinical messaging standard. HL7 is a syntax used to exchange clinical and administrative information--e.g., lab results, diagnosis, admissions, and discharges--between health information systems.

The acronym HL7 is most often used to refer to the messaging standard, but it is also used to refer to the organization that develops and supports the standard. That's in contrast to most other health IT standards like the International Classification of Disease (ICD), developed by an organization with a separate identity, the World Health Organization (WHO).

The core of the HL7 standard is the Reference Information Model (RIM)-a large pictorial representation of the clinical data (domains) that identifies the life cycle of events that a message or groups of related messages will carry. It is a shared model between all the domains and as such is the model from which all domains create their messages.

The HL7 v3 standard also specifies the Clinical Document Architecture (CDA), an XML-based markup schema for specifying the encoding, content, and structure of clinicaldata documents for exchange among data provider and data consumer applications. The Continuity of Care Document (CCD) is an example of a document type that conforms to the HL7 CDA specification.

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