Scrutinizing the relationships between SNOMED CT concepts and semantic tags

The fully specified name of a concept in SNOMED CT is formed by a term to which in the typical case is added a semantic tag (ST). An ST is meant to disambiguate homonymous terms and indicate where that concept fits into SNOMED’s massive concept hierarchy. We have developed a method to determine whether or not a concept’s tag correctly identifies its place in the hierarchy, and applied this method to an analysis of all active concepts in every SNOMED CT release from January 2003 to January 2017. Our results show that there are concepts in every release whose tags do not match their placement in the hierarchy. These tag/hierarchy mismatches appear to be errors. The number of such errors is increasing in recent versions.