The impact of SNOMED CT revisions on a mapped interface terminology: terminology development and implementation issues.

Large-scale mapping efforts have been done in attempts to migrate systems that use proprietary concepts to ones that use terminological standards such as SNOMED CT. As efforts move towards implementation, the target maps should retain a predictable structure including those targets requiring post-coordination of SNOMED CT concepts. In this paper, we compared the editorial guidelines of two versions of SNOMED CT (January 2005 and July 2006, respectively) and noted how the revisions affected a single, comprehensive set of mapped concepts (n=2002) from a legacy system. Changes made to the categories and guidelines for approved attributes were noted and then evaluated against the post-coordinated maps (n=1570) from the original mapping effort. Seventy-one percent (n=1118) of the concepts were affected due to changes made in either SNOMED CT categories or to the revision of approved attributes. While the efforts of each subsequent SNOMED CT version aim for continual improvement, changes made to its core structure and post-coordination guidelines make it more difficult to migrate proprietary data to this reference standard. Attention must be paid to auditing the processes used in terminology development to include the impact that their revisions may have on real-world clinical implementation.