SNOMED® was developed by the College of American Pathologists (CAP).
resulted from a merger between SNOMED-RT (Reference Terminology)
(strong in in specialty medicine)
and the England and Wales National Health Service's Clinical Terms
(a UK-based terminology for primary care previously known as the Read Codes).
SNOMED CT is considered to be the first international terminology.
A new international organisation, the Health Terminology Standards Development
Organisation (IHTSDO®, also known as SNOMED SDO®) acquired the ownership
of SNOMED Clinical Terms (SNOMED CT®) on 26 April 2007 and will be responsible
for future maintenance and development.
background / derivation
The CAP introduced SNOMED® in 1977.
SNOMED derived from SNOP (Systemized Nomenclature of Pathology)
which was introduced in 1965 and expanded this lexicon to include all of
Further significant revisions included SNOMED-II in 1979 and
SNOMED-III (International) in 1993. SNOMED-RT
succeeded SNOMED version 3.5 (1998), and
included over 340,000 explicit relationships.
SNOMED-RT represented a significant update whilst remaining compatible with SNOMED
International, presenting data in a completely machine-readable format.
What had previously been a relatively flat, multi-axial system became a true semantic network.
SNOMED CT is probably the most comprehensive medical terminology developed to date and
can be used to support patient data capture, transfer,
querying and storage via an electronic patient record.
Includes a Semantic Net of over 300,000 medical concepts and their relationships
Multiple axes and hierarchies
At the top level are 3 main hierarchies (Finding, disease procedure) and 15 supporting hierarchies
Over 7 million relationships are defined
Uses a description logic (KRSS) as the basis for its concept representation
Includes concepts covering multiple use scenarios: diagnosis, drug definitions, findings, procedures, anatomy ...
Many other terminologies can map to SNOMED CT including LOINC and ICD9.
SNOMED CT has been licenced in at least 30 countries worldwide.
A 5 year renewable licence agreement between the CAP and "the [US] National Library of Medicine (NLM), provides free access to the English and Spanish language editions of the SNOMED CT Core content and all version updates through the NLM's UMLS Metathesaurus, which is a knowledge source containing biomedical concepts and terms from approximately 100 source vocabularies and classifications".
SNOMED CT has been adopted as the preferred terminology of the England and Wales NHS.
SNOMED CT is integrated in commercial electronic medical record systems such as Cerner Millennium.
We describe the framework for SNOMED RT (Reference Terminology), designed to complement the broad coverage of medical concepts in SNOMED with a set of enhanced features that significantly increases its value as a reference terminology for representing clinical data. We describe what is meant by a reference terminology, and differentiate SNOMED RT from specialized terminologies that enable user interfaces, electronic messaging, or natural language processing, as well as from other specialized reference terminologies whose primary purpose is for representing data that is not primarily clinical in nature. We then describe how SNOMED RT represents multiple hierarchies and incorporates description logic. We believe that such a comprehensive set of concepts at multiple levels of granularity, with multiple logic-based subsumption hierarchies can meet the requirements of a reference terminology for health care.
Wang AY, Sable JH, Spackman KA.
The SNOMED Clinical Terms Development Process: Refinement and Analysis of Content.
Proc AMIA Symp 2002;:845-9.
SNOMED (R) Clinical Terms is a comprehensive concept-based health care terminology that was created by merging SNOMED RT (R) and Clinical Terms Version 3. Following the mapping of concepts and descriptions into a merged database, the terminology was further refined by adding new content, modeling the relationships of individual concepts, and reviewing the hierarchical structure. A quality control process was performed to ensure integrity of the data. Additional features such as subsets, qualifiers, and mappings to other coding systems were added or updated to facilitate usability. We then analyzed the content of the completed work. This paper describes the refinement processes and compares the actual content of SNOMED CT (R) with the early data obtained from analysis of the description mapping process. As predicted, the majority of concepts in SNOMED CT originated from SNOMED RT or CTV3, but not both.
Normal forms for description logic expressions of clinical concepts in SNOMED RT.
Proc AMIA Symp 2001;:627-31.
Modern clinical terminologies organize concepts into multi-hierarchy structures that are defined by logic-based expressions, enabling compositional representation of clinical statements and supporting more complete and consistent retrieval of clinical data. The Systematized Nomenclature of Medicine, Reference Terminology (SNOMED RT) gives each concept code a semantic definition stated in description logic. The process of development, testing and distribution of these definitions has highlighted the fact that a concept definition may take many different but logically equivalent forms, and has revealed a need for a set of normal forms for authoring, distribution, and other purposes. This paper describes the difference between a choice of syntax and a choice of normal form, and defines several different normal forms, including a short canonical form, a long canonical form, and a distribution normal form.
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