Objective. To evaluate the clinical utility of various diagnostic tests, two enzyme immunoassays and a chemiluminescent DNA probe were compared with cell culture (with monoclonal antibody confirmation) for the diagnosis of endocervical Chlamydia trachomatis infection.
Design. The clinical performance of four diagnostic methods for Chlamydia trachomatis urogenital infections were compared, using specimens generated from consecutive pelvic examinations.
Setting. Subjects were recruited from an urban adolescent clinic that provides primary and referral care.
Participants. A total of 479 adolescent female subjects were enrolled. The order of sample collection was randomized. Subjects were stratified according to whether they were asymptomatic (n = 228) or symptomatic (n = 251).
Measurements and results. Discrepant analysis was performed when culture was negative and nonculture technique was positive. The subject was considered to have chlamydia if culture was positive, or if one or more nonculture techniques, with that test's confirmatory assay, were positive (consensus-positive). Prevalence of chlamydia was 11.0% in the asymptomatic, and 20.7% in the symptomatic, group. Overall, 32.5% of the infected subjects were asymptomatic. Sensitivity of diagnostic methods varied from 52% to 80% in the asymptomatic subjects, compared with 65% to 81% in symptomatic subjects. Culture sensitivity was 75% to 80%. The specificities of all tests were 96% or greater. Accuracy of nonculture methods varied from 89.5% (DNA probe, symptomatic subjects) to 96.9% (enzyme immunoassay asymptomatic subjects).
Conclusions. There are significant differences in symptomatic subjects when evaluating accuracy of test outcome, using a consensus-positive criterion. Asymptomatic infections account for nearly one third of adolescent females infected with chlamydia. The prevalence of chlamydia urogenital infections are underestimated by any single diagnostic test, particularly in the asymptomatic patient.