Clinical Diagnosis and the Order of Information

Background. Information order can influence judgment. However, it remains unclear whether the order of clinical data affects physicians' interpretations of these data when they are engaged in familiar diagnostic tasks. Methods. Of 400 randomly selected family physicians who were given a questionnaire involving a brief written scenario about a young woman with acute dysuria, 315 (79%) returned usable responses. The physicians had been randomized into two groups, and both groups had received the same clinical information but in different orders. After learning the patient's chief com plaint, physicians received either the patient's history and physical examination results followed by the laboratory data (the H&P-first group) or the laboratory data followed by the history and physical examination results (the H&P-last group). The results of the history and physical examination were supportive of the diagnosis of UTI, while the laboratory data were not. All physicians judged the probability of a urinary tract infection (UTI) after each piece of information. Results. The two groups had similar mean estimates of the probability of a UTI after learning the chief complaint (67.4% vs 67.8%, p = 0.85). At the end of the scenario, the H&P-first group judged UTI to be less likely than did the H&P-last group (50.9% vs 59.1 %, p = 0.03) despite having identical information. Comparison of the mean likelihood ratios attributed to the clinical information showed that the H&P-first group gave less weight to the history and phys ical than did the H&P-last group (p = 0.04). Conclusions. The order in which clinical information was presented influenced physicians' estimates of the probability of dis ease. The clinical history and physical examination were given more weight by phy sicians who received this information last. Key words: diagnosis; urinary tract infec tions ; judgment; primary care; clinical decision making. (Med Decis Making 1998;18: 412-417)