Use of multiple nucleic acid amplification tests to define the infected-patient gold standard in clinical trials of new diagnostic tests for Chlamydia trachomatis infections

Nucleic acid amplification tests (NAATs) can be used to define the infected-patient gold standard for the purpose of designing studies of the performance of Chlamydia trachomatis diagnostic tests. It is unclear how many test results run by different NAATs and what combinations of specimens comprise the best infected-patient gold standard. We approached this question with data from a large study of the performance of a new NAAT. Data were available from three endocervical swabs and a urine specimen collected from each of 1,412 women and tested by three different NAATs. Results from all three assays were used equally in a rotating fashion to define the infected-patient gold standard. Multiple different infected-patient gold standards for estimating swab and urine specimen sensitivity and specificity for one NAAT method were created by varying the number and combinations of swab and urine comparator results with two different NAATs, The effect of changing the infected-patient gold standard definition was determined by constructing receiver-operator-like curves with calculated sensitivities and specificities for each test. The one-positive-of-two-results or two-positive-of-two-results (same or two different assays) infected-patient gold standard definitions produced low sensitivity and low specificity estimates, respectively. If four comparator NAAT results were used, the any-three-positive-of-four-results definition or the at-least-one-specimen-positive-by-each-of-two-comparator-assays definition appeared to provide better combinations of sensitivity and specificity estimates. The any-two-positive-out-of-three-results definition resulted in estimates that were as good as produced with the former two definitions. This analytic approach provides a means of clearly visualizing the effects of changing NAAT-based infected-patient gold standards and should be helpful in designing future studies of new C. trachomatis diagnostic tests.