EVALUATION OF THE GEN-PROBE PACE 2 AND THE MICROTRAK ENZYME-IMMUNOASSAY FOR DIAGNOSIS OF CHLAMYDIA-TRACHOMATIS IN UROGENITAL SAMPLES

Background and Objectives: The aim of the study was to investigate the value of the Gen-Probe PACE 2 assay for routine diagnosis of Chlamydi a trachomatis in genital specimens of symptomatic and asymptomatic men and women patients. Study Design: Samples were collected from 90 men and 299 women patients and tested by using the Gen-Probe assay and the EIA MicroTrak. Discrepant results were further analyzed by immunofluo rescence, a second run of the Gen-Probe assay, and a probe competition assay (PCA) to establish the number of true positive and negative out comes based on the two tests used. Results: The overall prevalence of C. trachomatis was 8.5% in all patients tested (women: 3.7%, men: 13.3 %) with an overall agreement of 95.4% between the two diagnostic metho ds. Of the 18 discordant results, 12 (67%) were considered to be false positive in the Gen-Probe assay and 3 (16%) false positive in the EIA . Two (11%) positive results were missed in the Gen-Probe assay and 1 (6%) in the EIA, all observed in female specimens. The sensitivities a nd specificities of the EIA were 91.7% and 100% for men and 100% and 9 9% for women, and for the Gen-Probe assay were 83.3% and 100% for men and 100% and 95.8% for women, respectively, when compared with true po sitive and true negative results. Although the predictive value for al l positive results (PVP) was 88% for the EIA and 78.2% for the Gen-Pro be assay, it was only 47.8% for positive female samples when using the Gen-Probe assay. Conclusion: The Gen-Probe assay revealed a sensitivi ty comparable with the EIA. The accuracy of test results provided by a single Gen-Probe assay was considerably lower than by Micro-Trak redu cing the utility of PACE 2 as a diagnostic technique for Chlamydia dia gnosis. Due to the high rate of false-positive samples in the Gen-Prob e assay, positive results with a low value of relative light units hav e to be further analyzed by confirmation procedures.