[Evaluation of physicians' decision making processes in primary care medicine]

To investigate how primary care physicians select appropriate diagnostic tests in their clinical practice, we analyzed the physician's decision making processes by means of written case simulations. We allocated the physicians who participated in this study to three groups; nine residents and ten attending physicians from the Department of Primary Care Medicine, and nine specialists from the Department of Medicine in our hospital. After they read a history and findings in each presented case, the physicians were requested (1) to make diagnostic hypotheses and predict probability of each hypothesis, (2) to select diagnostic tests and their purpose, and (3) to estimate contribution of the tests to the diagnosis. The results revealed that the attending physicians tended to order the diagnostic tests more strictly based on their hypotheses than the residents and specialists did. The attending physicians selected diagnostic tests from specific varieties rather than from "Essential Laboratory Tests" when they were confident in their hypotheses. On the other hand, they selected the tests mainly from "Essential laboratory Tests" when they were uncertain of diagnosis or needed to exclude serious diseases. They regarded the contribution of tests to the diagnosis as high when specific diagnostic tests were available for the presumptive diagnosis, or severe conditions were expected. These findings suggest that, in the setting of primary care practice, the application of laboratory tests depends on the severity of presenting conditions and pre-test certainty of the diagnostic hypothesis. Therefore, it may not be always appropriate to apply "Essential Laboratory Tests" uniformly to every patient irrespective of his/her condition.