Comparison between cell culture and serology for detecting Chlamydia trachomatis in women seeking abortion

The efficiency of an immunoperoxidase serological assay and culture of Chlamydia trachomatis were compared in 127 women seeking first trimester abortion. Serum IgG and IgA antibodies specific for C trachomatis were detected by a single serovar (L2) inclusion immunoperoxidase assay (IPA). Eighty (63%) women were seropositive for chlamydial IgG and 31 (24%) for IgA antibodies. C trachomatis was isolated from 21 of 127 (17%) women. Twenty of the 80 women (25%) seropositive for specific IgG antibodies and one of 47 (2%) patients without these antibodies were culture positive (p < 0.001). Compared with isolation, chlamydial antibodies at a titre of ≥ 16 showed high sensitivity and negative predictive value (95% and 98%, respectively), but low specificity and efficiency (43% and 52%, respectively). Chlamydial IgA antibodies at a titre of ≥ 8 showed low sensitivity (52%), but a higher specificity, negative predictive value, and efficiency of 81%, 90%, and 76%, respectively. C trachomatis IgG antibodies at a titre of 16 as determined by IPA can be used as an efficient negative exclusion marker for active chlamydial infection in screening women seeking abortion.