Evaluation of fluorescein-conjugated monoclonal antibody test to detect Chlamydia trachomatis endocervical infections in adolescent girls

Abstract

We evaluated the fluorescein-conjugated monoclonal antibody (FA) test for screening for Chlamydia trachomatis endocervical infection in a general adolescent clinic. Three hundred sixty-three consecutive adolescent girls, ages 13 to 20 years (mean 17.3 years) were examined. Forty-five (12%) FA smears had insufficient cells. Reason for visit included non-lower genital tract-related disorders in 241 (76%) girls, and lower genital tract-related disorders in 77 (24%). C. trachomatis was isolated by tissue culture in 46 (14%) patients, and Neisseria gonorrhoeae by culture in 22 (7%), and Trichomonas vaginalis was identified by wet mount in 13 (5%). Compared with our tissue culture technique, the performance of the FA test was as follows: sensitivity 61% (28 of 46), specificity 97% (264 of 272), positive predictive value 78% (28 of 36), and negative predictive value 94% (264 of 282). There was no significant difference in test performance by race, although the sensitivity rate (64%) of the test in blacks was twice that (30%) in nonblacks. This apparent difference in test performance by race may actually represent variations in group characteristics, including exposure rate, susceptibility, and number of inclusion forming units available for tissue culture of Chlamydia in blacks compared with nonblacks. In our adolescent clinic, the tissue culture is superior to FA in detecting Chlamydia. We recommend that the FA test be used where tissue culture isolation for Chlamydia is not readily available, where known or predicted chlamydial infection rates are high, and where known or predicted numbers of inclusion forming units of Chlamydia in tissue culture are high.