Systematized Nomenclature of Medicine

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, procedures, microorganisms, substances, etc. It allows a consistent way to index, store, retrieve, and aggregate medical data across specialties and sites of care. Although now international, SNOMED was started in the U.S. by the College of American Pathologists (CAP) in 1973 and revised into the 1990s. In 2002 CAP's SNOMED Reference Terminology (SNOMED RT) was merged with, and expanded by, the National Health Service's Clinical Terms Version 3 (previously known as the Read codes) to produce SNOMED CT.

Versions of SNOMED released prior to 2001 were based on a multiaxial, hierarchical classification system. As in any such system, a disease may be located in a body organ (anatomy), which results in a code in a topography axis and may lead to morphological alterations represented by a morphology code.

In 2002 the first release of SNOMED CT adopted a completely different structure. A sub-type hierarchy, supported by defining relationships based on description logic, replaced the axes described in this article. Versions of SNOMED prior to SNOMED CT are planned to be formally deprecated from 2017. Therefore readers interested in current information about SNOMED are directed to the article on SNOMED CT.

SNOMED was designed as a comprehensive nomenclature of clinical medicine for the purpose of accurately storing and/or retrieving records of clinical care in human and veterinary medicine. The metaphor used by Roger A. Côté, the first editorial chair, was that SNOMED would become the periodic table of elements of medicine because of its definitional organization beyond the hierarchical design. Indeed, diseases and procedures were ordered hierarchically and are further referenced back to more elementary terms (see Reference Ontology and Multi-Axial Design, below).

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