Evaluation of Abbott Testpack® Chlamydia for Detection of Chlamydia trachomatis in Patients Attending Sexually Transmitted Diseases Clinics

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Abstract
This work compared a rapid solid-phase EIA (Abbott TestPack Chlamydia) to tissue culture and a direct fluorescent antibody test (Syva Microtrak) for detection of C. trachomatis in 436 patients attending two inner-city sexually transmitted diseases (STD) clinics. The prevalence of C. trachomatis by culture was 12% (5% in men, 15% in women). Overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TestPack compared to culture were 70%, 98%, 80%, and 96% respectively. In men, 12 specimens were positive by TestPack, while only eight specimens were positive by culture. Six TestPack-positive, culture-negative specimens were further evaluated by centrifugation of culture transport media and examination of the sediment for chlamydia elementary bodies (EBs) using fluorescent monoclonal antibodies to C. trachomatis. Using this procedure, five of six culture negative specimens contained EBs (revised sensitivity 85%, specificity 99%, PPV 92%, NPV 99%). In 285 women evaluable in culture and TestPack, 44 (15%) specimens were culture positive; TestPack was positive in 29 (sensitivity 66%) culture positive women. Of 241 culture negative patients, 238 had negative TestPack results (specificity 99%) and no EBs were detected in the culture-negative, TestPack-positive specimens. Twenty-three (8%) Microtrak specimens were unsatisfactory for testing; two of these were culture and TestPack positive. Therefore, of 263 specimens evaluable using Microtrak, 42 (16%) specimens were culture positive; Microtrak was positive in 32 (sensitivity 76%) culture-positive women. Abbott TestPack Chlamydia is a rapid (25 minute), visually read format requiring no specialized equipment for detection of chlamydia infections with a sensitivity comparable to that of Microtrak.