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Tuesday, 17 October 2006


Olga Kostopoulou, PhD, MSc1, Jurriaan Oudhoff, PhD, MSc1, Radhika Nath1, Craig W. Munro, M.B.Ch.B.1, Brendan Delaney1, and Clare Harries, PhD, BA2. (1) University of Birmingham, Birmingham, United Kingdom, (2) University College London, London, United Kingdom

PURPOSE: Elstein et al. (1978) emphasized the lack of a general problem solving ability in clinical diagnosis and the importance of problem features in determining performance. A crucial problem feature is difficulty, but it is usually defined post hoc (number of errors made) in studies of clinicians' diagnostic performance. A taxonomy of difficulty would allow us systematically to create/select diagnostic problems and formulate predictions for study. Such a taxonomy was developed for a study of diagnosis in Family Medicine a specialty characterized by non-specific presentations and low prevalence of serious disease. METHODS: Categories of difficulty were derived from the psychology literature on diagnosis. They were refined, contextualised and exemplified using information from medico-legal databases, the clinical literature on diagnostic error, and interviews with family physicians. RESULTS: Diagnostic difficulty presupposes competing hypotheses. Additional difficulty comes from the way disease presents, its prevalence, and interaction with features of human reasoning: the tendency to look for and recognize familiar patterns in the presented information, and to ignore or explain away information that does not fit a recognized pattern; the base-rate heuristic and the associated biases, availability and representativeness; the tendency to assume that there is only one cause for the presenting symptoms. The emerging taxonomy has the following structure: A. No easily discernible pattern in the initial patient presentation: 1) patient presents with non-specific symptom; 2) patient presents with multiple symptoms that do not make a pattern. B. A pattern can be discerned in the initial patient presentation, but 1) important features are inconsistent or missing; 2) there are distracting features; 3) the correct diagnosis is not the most prevalent; 4) there are coexisting diseases, independent or interacting. Categories of difficulty are not necessarily mutually exclusive and a patient presentation can contain more than one type of difficulty. Moreover, during diagnosis of a patient case, a clinician may pass from category A (not immediately discerning pattern) to B (pattern discerned). CONCLUSIONS: A taxonomy of diagnostic difficulty for Family Medicine was developed on the basis of psychological theory and empirical information on diagnostic error. The taxonomy aims to provide a basis for the systematic development of realistic scenarios for the study of medical diagnostic reasoning and help formulate predictions about the performance expected.

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See more of The 28th Annual Meeting of the Society for Medical Decision Making (October 15-18, 2006)