Use of receiver operating characteristic curves to evaluate the clinical performance of analytical systems.

The usefulness of an analytical system in patient care is ultimately judged not by its analytical performance but by its clinical performance, i.e., its ability to separate apparently similar patients into two subgroups, one of which has a particular clinically important condition and another subgroup which does not. This clinical performance can be studied with the tools of signal detectability theory, originally developed to analyze the performance of radar and data-transmission systems. Each classification made by an analytical system may be categorized as a true-positive, true-negative, false-positive, or false-negative decision. For laboratory tests the proportion of decisions in each category depends on the biological overlap between the two subgroups, the analytical performance of the system, and the decision level chosen. The clinical performance of the analytical system for all possible decision levels is represented by the receiver operating characteristic curve, which plots the true-positive rate against the false-positive rate. The use of these curves permits comparison of alternative analytical techniques at equal true-positive rates and at all possible decision levels. These comparisons show the effect of analytical improvements on clinical performance.