An evaluation of pathologists' application of the diagnostic criteria from the San Diego definition of SIDS and unclassified sudden infant death

Despite being widely used, few studies have assessed the utility of the San Diego definition of sudden infant death syndrome (SIDS). The purpose of this study was to evaluate pathologists' application of the San Diego definition in all cases of sudden unexpected death in infancy (SUDI) that occurred in Queensland, Australia, between 2010 and 2014. Key coronial documents of 228 cases of SUDI were reviewed independently by three reviewers and classified according to the San Diego definition. Clear guidance regarding the evidentiary threshold for classification and interpretation of the San Diego definition was provided. All reviewers classified cases identically in 202 cases (88.6%). Consensus was achieved on the classification of the remaining 26 deaths following case discussion. After review, 79 cases were classified as SIDS, a one third reduction compared with the original classification, mainly due to a high probability of accidental asphyxia. The number of cases classified as undetermined (USID) almost doubled (75/228, 32.9%), and there was more than a fivefold increase in cases classified as asphyxia (43/228, 18.9%). Natural conditions decreased by approximately one third (21/228, 9.2%). This study demonstrates that with clear guidelines for interpretation, the San Diego definition can be applied reliably, with discrepancies resolved through a process of peer review.