Chlamydiazyme plus blocking assay to detect Chlamydia trachomatis in endocervical specimens

Three methods to detect Chlamydia trachomatis in endocervical swab specimens collected from 502 women with genitourinary or abdominopelvic symptoms were evaluated: (1) a direct immunofluorescence assay, (2) an enzyme-linked immunoabsorbent assay, confirming positive samples with a blocking assay, and (3) conventional tissue cell culture. C. trachomatis was detected by at least one method in 72 specimens, of which 56 (11%) were determined to be true-positive results by repeated testing and by performing a confirmatory assay. The sensitivity, specificity, and positive and negative predictive values were 91%, 100%, 100%, and 99%, respectively, for culture and the enzyme-linked immunoabsorbent assay plus blocking assay and 74%, 98%, 83%, and 96%, respectively, for the direct immunofluorescence assay. In this population of women, using the enzyme-linked immunoabsorbent assay with the confirmatory assay is a rapid, reliable, and cost-effective alternative to culture for diagnosing infection with C. trachomatis.