QUANTIFYING THE VALUE OF DIAGNOSTIC-TESTS

This paper considers the different statistics that can be derived from studies on the value of diagnostic tests. Well-accepted quantities, s uch as sensitivity and specificity, are reviewed and the Value of the likelihood ratio in communicating particular test results is highlight ed. A new quantity, the 'diagnostic value index', is proposed and vari ous examples of its application in nuclear medicine studies are presen ted. This new index is based on a weighted average of the likelihood r atios for all possible outcomes of the test, the average being weighte d according to how frequently a particular outcome occurs. This index provides an objective and quantitative means of comparing the diagnost ic value of different tests, or of comparing the value of a given test in different patient groups. It is hoped that this will be a useful a id to clinical decision-making concerning referrals for diagnostic tes ts. ((C) 1998 Lippincott Williams & Wilkins).