Diagnostic errors in three medical eras: a necropsy study

Background Studies comparing the accuracy of clinical diagnosis in unselect ed patients who died in hospital in different medical ems have shown no dec line of errors in the main diagnosis. We assessed changes in diagnostic acc uracy over 20 years. Methods We analysed retrospectively diagnostic errors, with use of necropsy as the gold standard for diagnosis. We randomly selected 300 patients who died at a tertiary-care teaching hospital in Switzerland-100 in each of 197 2, 1982, and 1992. We classified discrepancies between clinical diagnosis a nd necropsy findings as major and minor errors. Findings The overall necropsy rate at the hostpial stayed at around 90% for the whole period. During the study, the frequency of major discrepancies d eclined significantly (1972, 30%; 1982, 18%; 1992, 14%; p=0.007). The rate of minor diagnostic errors increased significantly from 23% in 1972 to 46% in 1992 (p<0.001). The increase in overall diagnostic accuracy occurred mai nly because of a significant improvement in specificity for cardiovascular diseases (1972, 85%; 1982, 82%; 1992, 97%; p=0.034) and nonsignificantly im proved sensitivity (1972, 69%; 1982, 82%; 1992, 86%; p=0.061). Sensitivity also improved for infectious diseases (1972, 25%; 1982, 67%; 1992, 86%; p=0 .036). Sensitivity and specificity for neoplastic diseases were high origin ally and did not change. The total number of diagnostic procedures per year increased from 191 in 1972 to 259 in 1992, mainly because of non-invasive techniques, such as ultrasonography, and endoscopies. Interpretation The frequency of major diagnostic errors in unselected patie nts who died in hospital was halved over 20 years, probably because of impr oved clinical skills and new diagnostic procedures.