Head-to-head evaluation of five chlamydia tests relative to a quality-assured culture standard

Nucleic acid amplification tests offer superior sensitivity for the detecti on of Chlamydia trachomatis infection, but many laboratories still use nona mplification methods because of the lower cost and ease of use, In spite of their availability for more than a decade, few studies have directly compa red the nonamplification tests. Such comparisons are still needed in additi on to studies that directly compare individual nonamplification and amplifi cation tests. The purpose of this study was to evaluate and compare the per formance characteristics relative to culture of five different tests for th e detection of C. trachomatis with and without confirmation of positive res ults. The tests were applied to endocervical specimens from 4,980 women att ending family planning clinics in the northwestern United States, The five nonculture tests included Chlamydiazyme (Abbott), MicroTrak direct fluoresc ent antibody (DFA) (Syva), MicroTrak enzyme immunoassay (EIA) (Syva), Pace 2 (Gen-Probe), and Pathfinder EIA (Sanofi/Kallestad), All positive results obtained with a nonculture test (except MicroTrak DFA) were confirmed by te sting the original specimens with a blocking antibody test (Chlamydiazyme), a cytospin DFA (MicroTrak EIA and Pathfinder EIA), and a probe competition assay (Pace 2), The prevalence of culture-proven chlamydia was 3.9%. The s ensitivities of the nonculture tests were in a range from 62 to 75%, and si gnificant differences between tests in terms of sensitivity were observed. The positive predictive value for each test was 0.85 or higher, The specifi cities of the nonculture tests without performance of confirmations were gr eater than 99%, Performing confirmatory tests eliminated nearly all of the false positives.