Paolo WF, et al. - The objective of the authors was to determine the emergency physicians' estimated pre and posttest disease probabilities before and after computerized tomography (CT) scan results in patients with nontraumatic abdominal and pelvic pain. They compared the estimated post-test disease probabilities to the probabilities obtained for similar diagnostic tests as reported in the literature. Physicians tended to overestimate the power of CT scanning when applying the probability theory of disease. In diseases with good positive and negative likelihood ratios such as in diverticulitis, the difference in physician and actual post-test probabilities could be small or not clinically significant; however, in diseases with poor likelihood ratios such as in post-op abscess, this difference could be large and clinically significant.