Background: Appropriate diagnostic testing involves

considerations of cost-effectiveness. We examined the cost-effectiveness of individual tests in a panel of tests defined by the Japan Society of Clinical Pathology. Methods: We studied 540 new, symptomatic primary care outpatients with a set of 30 common diagnostic tests [the Essential Laboratory Tests (2); ELT(2) panel] for clinical evaluation and identification of occult disease. A useful result (UR) of testing was defined as a finding that contributed to a change in a physician’s diagnosis or decision-making relating to a “tentative initial diag-nosis ” obtained from history and physical examination alone. Results: The ELT(2) panel testing yielded 398 URs and uncovered 261 occult diseases among 540 patients. In total, 1592 tests contributed to either UR-generation o