A RECEIVER OPERATING - CHARACTERISTIC PARTIAL AREA INDEX FOR HIGHLY SENSITIVE DIAGNOSTIC-TESTS

PURPOSE: Area under a receiver operating characteristic (ROC) curve (A (z)) is widely used as an index of diagnostic performance. However, A( z) is not a meaningful summary of clinical diagnostic performance when high sensitivity must be maintained clinically. The authors developed a new ROC partial area index, which measures clinical diagnostic perf ormance more meaningfully in such situations, to summarize an ROC curv e in only a high-sensitivity region. MATERIALS AND METHODS: The mathem atical formulation of the partial area index was derived from the conv entional binormal model. Statistical tests of apparent differences in this index were formulated analogous to that of A(z). One common stati stical test involving the partial area index was validated by computer simulations under realistic conditions. RESULTS: An example in mammog raphy illustrates a situation in which the partial area index is more meaningful than A(z) in measuring clinical diagnostic performance. CON CLUSION: The partial area index can be used as a more meaningful alter native to the conventional A(z) index for highly sensitive diagnostic tests.