Applying Evolutionary Terminology Auditing to SNOMED CT.

Evolutionary Terminology Auditing is a technique designed to measure quality improvements of terminologies over successive versions. It uses the most recent version of a terminology as a benchmark and assumes that changes in the underlying ontology correspond to changes in either that part of reality that is covered by the terminology, or the authors' understanding - if not the 'state of the art' in general - thereof. Applied to SNOMED CT over 18 versions, it reveals that at the level of the concepts minimal improvements are obtained and that the second assumption holds for far less changes than one would expect. It is recommended that future versions of SNOMED CT provide more explicit documentation for each introduced change.