Cross-Mapping APACHE IV "Reasons for Intensive Care Admission" Classification to SNOMED CT

The APACHE IV classification is used to capture diagnostic information for calculation of mortality risks in intensive care (IC). The lack of structured and formal definitions for concepts in APACHE IV classification as in any classification results in shortcomings when scaling up for re-use. The use of SNOMED CT as a reference terminology can address these shortcomings. However, all of SNOMED CT contains large amounts of information that is irrelevant for IC. By building an interface terminology (IfT) based on SNOMED CT and APACHE IV, it is possible to isolate the IC users from the complexity of SNOMED CT while enabling standardized data registration. Within this study, a mapping is realized from the APACHE IV classification to SNOMED CT. The results of the mapping will be used to identify a relevant SNOMED CT subset for the development of an IC-specific IfT. The vast majority of the diagnostic categories in APACHE IV could be mapped to one or more SNOMED CT concepts (83.8%) and for the remaining concept a partial match was identified (16%). The good mapping results will provide a SNOMED CT subset sufficient for developing an IC-specific IfT. Finally, lessons learned in this study are valuable for other researchers who intend to realize a mapping from a classification to SNOMED CT.