Direct fluorescent antibody testing for endocervical Chlamydia trachomatis: factors affecting accuracy.

Endocervical swabbings obtained after two previous cleansing swabs from 202 women with indications for testing for genital chlamydial infection were evaluated for the presence of Chlamydia trachomatis by culture and two direct fluorescent monoclonal antibody tests. In comparison with culture, the two direct fluorescent antibody tests showed sensitivities of 37.5 and 56.5% and specificities of 97.0 and 99.4% when read by experienced microbiology technologists recently trained in chlamydia direct fluorescent antibody interpretation and blinded to culture results. Overall sensitivities of 69.6 and 78.3% for the direct fluorescent antibody tests were obtained by an expert interpreter during discrepancy analysis. When only direct fluorescent antibody test specimens from the first swab after endocervical cleansing were considered, recently trained interpreters obtained sensitivities of 53.8 and 69.2%, and both direct fluorescent antibody tests were 100% sensitive for the expert interpreter. These data emphasize the critical importance of observer expertise and swab order to the accuracy of chlamydia direct fluorescent antibody tests. Previous studies of these tests are examined to determine how these factors and others may have influenced the outcome.