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Unified Medical Language System® (UMLS®)

2008AB SNOMED CT Source Information

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The Systematized Nomenclature of Medicine-Clinical Terms (SNOMED CT®) was originally created by the College of American Pathologists by combining SNOMED RT and Clinical Terms Version 3. SNOMED CT intellectual property rights were transferred to the SNOMED Standards Development Organisation (SDO) in the formal creation of the IHTSDO (International Health Terminology SDO).

SNOMED CT aims to improve patient care through the development of systems to record health care encounters accurately.

SNOMED CT provides the core general terminology for the electronic health record (EHR). The concepts have unique meanings and formal logic-based definitions organized into hierarchies. Each International Release includes the core of the terminology (concepts, descriptions, and relationships), together with works to support the implementation and use of SNOMED CT, including subsets, cross maps to existing classifications and coding schemes, and an extensive set of guidelines.

SNOMED CT includes more than 311,000 unique concepts. There are almost 800,000 descriptions in SNOMED CT, including synonyms that can be used to refer to a concept. In addition, there are approximately 1,360,000 links or semantic relationships between the SNOMED CT concepts.

UMLS licensees may download the SNOMED CT International Release files.

Metathesaurus Scope
The Metathesaurus representation of SNOMED CT includes the International Release, as well as ICD-9-CM Cross Maps, and data from the History files, US and UK Language subsets.

The Metathesaurus also includes the Spanish translation of the descriptions from the International Release (SNOMED CT Spanish).

SNOMED CT is used by standards setting organizations and in a variety of health care applications. It is also utilized by developers of electronic health data exchange applications.

Update Frequency
The SNOMED CT International Release is updated in January and July.

Metathesaurus Update Frequency
SNOMED CT is an updated source in each Metathesaurus release.

Sites Consulted

  1. International Health Terminology Standards Development Organisation [Internet]. Copenhagen: International Health Terminology Standards Development Organisation. SNOMED CT; [cited 2008 Sep 17]. Available from:; About SNOMED CT:; SNOMED CT components:; Release of SNOMED CT: