Screening for Chlamydia trachomatis infection in a pregnancy counseling clinic

Five hundred twenty asymptomatic women attending a pregnancy counseling clinic were interviewed and screened for cervical Chlamydia trachomatis infection before therapeutic abortion. Overall, 56 (10.8%) women were culture positive for C. trachomatis. Restricting testing to women with risk factors for infection or who had cervical leukocytosis on Gram staining of cervical mucus, or who were seropositive for C. trachomatis antibodies proved impractical because of insensitivity or nonspecificity. We evaluated three chlamydia diagnostic tests to determine which test had the best performance characteristics. In comparison with culture, the direct fluorescent antigen test had a sensitivity of 89% and a positive predictive value of 78%, whereas the enzyme immunoassay had 96% and 69%, respectively. When analysis was redone with any two positive laboratory tests to define true infection status, the performance parameters of enzyme immunoassay were sensitivity 98%, specificity 98%, and positive predictive value 87%. We conclude that all women undergoing therapeutic abortion require testing for C. trachomatis infection and that enzyme immunoassay is the most effective and practical test in this group of women.