The Systematized Nomenclature of Medicine -- Clinical Terms (SNOMED CT) is one of the most extensive terminology systems available. Its development represents collaboration between the College of American Pathologists (CAP) and the United Kingdom's National Health Services. The development of SNOMED CT can be been traced back to 1928 when the New York Academy of Medicine convened a forum to develop a new model for representing diseases and procedures.10 That multi-axial system eventually became the Standard Nomenclature of Diseases and Operations (SNDO) and provided the foundation for modern clinical terminologies. A consistent goal of all subsequent developers of the SNOMED works has been a terminology that is comprehensive enough for indexing the entire medical record.
SNOMED CT is structured in a way that emphasizes a computer readable format. A description logic based formalism supports navigation throughout the multiple hierarchies and allows for the composition of atomic level terms into more complex terms. The most recent version, SNOMED CT July 2002 Release, was used in this study and includes 330,000 concepts, 850,000 synonyms, and 50,000 semantic or defining relationships, for a total of over 1,000,000 terms. This terminology coding system is specifically designed to be embedded or enabled within computer based systems; a browser enables human navigation of the SNOMED CT hierarchies (www.snomed.org).
SNOMED CT was included in this study because it is a formal terminology and has the potential to serve as a convergent or reference terminology. The core data structure in which SNOMED CT is distributed includes a concepts table, a descriptions table, and a relationships table. SNOMED CT is available for use through an annual, renewable license and is distributed in a variety of electronic formats. There are ongoing discussions concerning between the federal government and CAP, that if ratified, would make SNOMED CT generally available for health care use in the U.S.