Performance of microtrak direct test for Chlamydia trachomatis in a prevalence study

Three hundred thirty-two women, aged 18-30 yr. attending two clinics in Burlington Vermont were screened for infection with Chlamydia trachomatis by two methods. Microtrak Direct Test (SYVA) and cell culture. The overall sensitivity for Microtrak compared with culture was 75% (18 of 24), the specificity was 99.7% (307 of 308), the positive predictive value was 94.7% (18 of 19), and the negative predictive value was 98.1% (307 of 313). Prevalence of Chlamydia trachomatis in this population was estimated to be 7.2% (95% confidence intervals 4.4-10.0). The results from this study suggest that Microtrak is less sensitive when used in unselected patient groups from populations of lower prevalence, in contrast to higher sensitivities previously reported.