Physician tolerance for uncertainty. Use of liver-spleen scans to detect metastases.

To gain insight into diagnostic test use, we interviewed 42 physicians who ordered 62 liver-spleen scans to detect possible metastases. Before receiving the actual scan results, physicians gave (1) pretest probability estimates for liver metastasis; (2) probability estimates and management plans given the most common scan results; and (3) probabilities above and below which they would stop the diagnostic workup (their decision thresholds). After learning the actual scan results, physicians gave their posttest probabilities and management plans. Thirteen physicians (31%) desired absolute certainty to rule in metastasis. Fifty percent planned further evaluations even when probability estimates of metastasis reached one of their probability targets for ending the workup. Greater attention to decision thresholds may improve physicians' understanding of their tolerance for diagnostic uncertainty and the ability of diagnostic tests to reduce it.