ABSTRACT
Clinicians use probabilistic reasoning at several stages in the diagnostic process. Remember that clinicians must, however, always consider the full clinical picture. In the refinement stage of the diagnostic process, clinicians are again unlikely to calculate probabilities explicitly but generally compare their knowledge of the characteristics of diseases and predictive combinations with the characteristics of the patient. European League Against Rheumatism has suggested that a combined approach taking into account clinical findings and presentation, risk factors elicited and radiographic features should be employed to diagnose Osteoarthritis. In terms of refining the differential diagnosis, the clinician first needs to know or have an idea of the ‘pretest probability’ that a patient has a condition based on the information they have gleaned from the history and examination. This primarily comes through experience of patients with similar conditions and knowledge of the working context.
