A new method to assess the difficulty of a medical diagnosis: application to electrocardiographic interpretation

A new method to assess the relative difficulty of a medical diagnosis and the efficacy of a diagnostic procedure is described. The cases within a population are classified by N independent interpreters, i.e., medical experts or computer programs. The percentages of correctly diagnosed cases by N (unanimity), N-1, N-2, ..., zero interpreters, respectively, are calculated. These N + 1 percentages are presented in a histogram. A cumulative plot is derived from the "unanimity" value. The ratio "unanimity value"/"zero value" is proposed as an index of diagnostic performance. An application to the CSE database is presented which is composed of 1,220 electrocardiographic tracings interpreted by 13 cardiologists and 15 computer programs. The cumulative plots, the performance index and Log (index) values, established for eight different diagnostic statements, clearly show the relative degree of diagnostic difficulty for each of them and the particular efficacy of each approach, i.e., electrocardiography versus vectorcardiography, and computerized versus human interpretation.