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Medical terminologies

Medical terminologies: SNOMED CT®
name Systematized Nomenclature of Medicine - Clinical Terms®
summary SNOMED® is a coding system, controlled vocabulary, classification system and thesaurus.
clinical focus Comprehensive clinical terminology. Designed to "capture information about a patient's history, illnesses, treatment and outcomes"
introduced 2001 (?)
current version  bullet  SNOMED CT Core Content and Release Highlights - July 2005
developed by SNOMED® was developed by the College of American Pathologists (CAP).

SNOMED CT 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 general medicine. 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.
  • standards  bullet  Standards organizations and government bodies that have recognised SNOMED CT as a standard
    in use 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.
    access Licence required.
    tools  bullet  Commercial tools from SNOMED  bullet  SNOB: freeware desktop SNOMED Browser  bullet  Mycroft: free, standalone, multi-terminology browser (USA only) [OC]  bullet  CliniClue medical terminologies browser [OC]
    international Translated into Spanish and German.
    College of American Pathologists. SNOMED, Systematized Nomenclature of Medicine. Chicago: Coll of Amer Pathol, 1994.

    []   []

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    Spackman K. SNOMED RT and SNOMED CT. Promise of an international clinical terminology. MD Comput 2000 Nov-Dec;17(6):29.

    [PubMed]   []

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    Spackman KA, Campbell KE, Côté RA. SNOMED-RT: a reference terminology for health care. Proc AMIA Annu Fall Symp. 1997;:640-4.


    " 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. "
    Spackman KA. 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. "
    contact IHTSDO®
    Rued Langgaards Vej 7, 5
    2300 Copenhagen S

    E: info(at)
    T: +45 36 44 87 36

    links  bullet  IHTSDO®  bullet  SNOMED - Systematized Nomenclature of Medicine  bullet  SNOMED CT  bullet  SNOMED CT brochure  bullet  SNOMED Clinical Terms on NHS Connecting for Health  bullet  CAP/NLM License Agreement for SNOMED CT  bullet  Introduction to SNOMED Clinical Terms and its use with HL7. HL7 Presentation by Bob Dolin, October 2004  bullet  SNOMED CT introduction by Enrico Coiera (taken from Guide to Health Informatics, Arnold, 2003) (AHIC)  bullet  Cerner Millennium
    page history
    Entry on OpenClinical: 15 July 2005
    Last main updates: 29 July 2005; 01 June 2007

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