Comparison of a fluorescent monoclonal antibody assay and a tissue culture assay for routine detection of infections caused by Chlamydia trachomatis.

The applicability of a commercial direct immunofluorescent monoclonal antibody assay for detection of Chlamydia trachomatis elementary bodies was studied on endocervical smears from 506 women attending a venereal disease clinic. The aim of this prospective examination was to simulate a daily routine. The results were compared to those of a well-functioning tissue culture assay. The overall positivity was 22.7%. Based on a positivity criterion of greater than or equal to 1 elementary body in the fluorescent antibody assay, the two assays agreed in 84.8% of the cases. In 50 specimens the antibody assay was positive and the culture assay negative, whereas in 23 the culture assay was positive and the antibody assay negative. The positive predictive value was 63.8%. Most of the discrepancies were found in specimens containing few elementary bodies or inclusions. Based on a criterion of greater than or equal to 10 elementary bodies, the positive predictive value was 70.9%, but the sensitivity fell to 67.5%.