SNOMED CT revisions and coded data repositories: when to upgrade?

SNOMED CT is gaining momentum in its acceptance and operational application as a reference terminology in electronic health systems. Because it is revised every six months, organizations using SNOMED CT might feel a need to ensure that their systems are synchronized with these revisions. It has been shown that for certain sorts of applications migration to a new version is a labor-intensive process. Here two indicators - the evolution of the global information content of an ontology over consecutive versions, and the perseverance of suspicious events - are proposed to assess whether it is worthwhile upgrading when a new version is released. The indicators can be computed automatically when a new version is released and are statistically unrelated. Trend breaks in their evolution are suggestive for the possible benefit of an upgrade and their predictive power correlates well with the retrospective realism-based quality metric which forms the basis of Evolutionary Terminology Auditing.