Patient-Oriented Performance Measures of Diagnostic Tests

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Abstract
Assignment Potential (AP) is a performance measure of a diagnostic test, characterizing the chance that, as a consequence of performing the test, the probability of disease will exceed a decision threshold, thereby permitting a management action to be taken. Another performance measure, Assignment Strength (AS) characterizes the average extent to which a decision threshold will be exceeded when the post-test probability of disease does exceed the threshold. Both AP and AS are functions of prior probability of disease and decision threshold, and can be represented as two-dimensional contour maps indicating their behavior throughout the entire probability and threshold space. AP and AS can be determined for both discrete-valued tests and tests with continuous spectra of results. The contour map displays facilitate determination of the values of these measures at any prior probability and threshold, as well as visual sensitivity analysis for ranges of prior probability and/or threshold. AP and AS may be useful to the clinician in prospective evaluation of a diagnostic test in situations where formal decision analysis is not feasible.