Comparative evaluation of detection assays for Chlamydia trachomatis

The performances of a commercial nucleic acid hybridization test (Gen-Probe Pace 2 Chlamydia trachomatis) and two commercial enzyme immunoassays (EIAs) (Abbott Chlamydiazyme and Pharmacia Chlamydia EIA) were evaluated against cell culture for the detection of C. trachomatis infection, with cervical swabs obtained from 1,037 women visiting a public sexual health center. The positivity rate by cell culture was 4.7%. Sensitivity and specificity for each test were as follows: Gen-Probe, 95.8 and 98.3%; Chlamydiazyme, 80.4 and 99.3%; Pharmacia EIA, 80.8 and 99.1%. Analysis of discrepant results with probe confirmation assay (Gen-Probe) and direct immunofluorescence (Syva Microtrak) revealed 12 cases of C. trachomatis infection for which culture was negative, resulting in the definition of a true-positive case as opposed to a culture positive. The positivity rate by true-positive definition was 5.9%, and sensitivity and specificity for each test were as follows: Gen-Probe, 96.7 and 99.6%; Chlamydiazyme, 77.5 and 100%; Pharmacia EIA, 77.0 and 100%; cell culture, 80.0 and 100%. We conclude that the Gen-Probe Pace 2 C. trachomatis test is a sensitive and specific alternative to cell culture for the detection of C. trachomatis.