COMPARING 2 DIAGNOSTIC-TESTS AGAINST THE SAME GOLD-STANDARD IN THE SAME SAMPLE

Methods are proposed for comparing two diagnostic tests for the same d ata where a threshold for positive for each test is specified. One met hod contrasts the diagnostic tests' estimated risks. A. second method compares the two tests' kappa coefficients. When thresholds for positi ve test results are specified a priori, maximum likelihood estimators and their asymptotic variances are derived and test statistics are pre sented for both case-control and naturalistic methods of sampling. The bootstrap is proposed as a method to assess differences in risk estim ators when thresholds for positive test results are chosen by scanning the data. Examples are given to illustrate the methods.