Understanding differential diagnostic disagreement in pathology

The Diagnostic Encyclopedia Workstation (DEW) was developed to support pathologists in diagnosing ovarian tumors. In this evaluation study, we had pathologists at several levels of experience diagnose a number of cases using either books or the DEW. In the context of this study, we needed a standard by which to measure performance of these pathologists. We, therefore, had experts enumerate for each test case the diagnoses they considered morphologically similar. To our surprise, the resulting lists of the experts varied considerably. The differential diagnosis of a disease based on its morphological characteristics, however, constitutes important reference knowledge in solving diagnostic problems. The question rose why the experts differed so much in their differential diagnostic knowledge. The ontogeny of a pathologist's personal knowledge is discussed and used to derive a model that can explain the limited consensus in differential diagnosis. The model helps to identify factors that may cause pathologists to diverge and others that may cause them to converge with respect to their knowledge. Strategies are proposed that are useful in achieving a better (differential) diagnostic consensus.