CONFIRMATION OF THE SYVA MICROTRAK ENZYME-IMMUNOASSAY FOR CHLAMYDIA-TRACHOMATIS BY SYVA DIRECT FLUORESCENT-ANTIBODY TEST

Background and Objectives: The Syva MicroTrak enzyme immunoassay (EIA) is used widely for screening women infected with Chlamydia trachomati s. Confirmatory tests used in conjunction with EIA screening have show n that false-positive results are common. Goals: To evaluate the speci ficity of the Syva MicroTrak EIA by confirmation of positive specimens with the Syva Direct Fluorescent Specimen Test. Study Design: Of 6,03 9 endocervical specimens collected from women attending Colorado famil y planning clinics, 328 positive EIA results (5.4%) were obtained by S yva MicroTrak EIA. A random subset of 136 positive specimens was teste d by Syva Direct Specimen Test. Twenty of 136 specimens (14.7%) negati ve by Syva Direct Specimen testing were also tested by Syva blocking a ntibody tests (9 of 20 positive, 45%) and Roche Amplicor polymerase ch ain reaction (PCR; 6 of 20 positive, 30%). Of 20 specimens positive by Syva MicroTrak EIA and negative by Syva Direct Specimen Test, 11 (55% ) were also negative by blocking antibody and PCR, including three spe cimens with initial EIA sample-to-cutoff ratios greater than 2. Conclu sions: Confirmatory testing of Syva MicroTrak EIA positive specimens w ith Syva Direct Specimen Test showed that 14.7% were false positive. C oupling the Syva Direct Specimen test with either blocking antibody or PCR reduces the rate of false-positive results to 8%.