Chlamydia trachomatis species specific serology: ImmunoComb Chlamydia bivalent versus microimmunofluorescence (MIF)

The ImmunoComb Chlamydia Bivalent IgG/IgA (Orgenics, Israel) is a new quantitative serologic test that employs LPS extracted Chlamydia trachomatis L2 and LPS extracted Chlamydia pneumoniae elementary bodies on two separate antigenic spots. The Bivalent C. trachomatis specific test results were compared with microimmunofluorescence (MIF), the gold standard of chlamydial species specific serology. For C. trachomatis IgG the Bivalent was highly concordant with the MIF: the rate of positive titres (IgG > or = 1:8) was 10% vs. 11% in 100 blood donors, 18% vs. 16% in 111 obstetric patients (6% antigen prevalence), 26% vs. 22% in sterile women with open (n = 54) and 86% vs. 84% with occluded (n = 51) tubes, and 88% vs. 85% in 103 women with C. trachomatis positive cervical smears. Surprisingly, the Bivalent differed considerably from the MIF in IgA prevalence: in obstetric patients (8% vs. 4%), sterile women with open (13% vs. 6%) and occluded (71% vs. 20%) tubes, and women with positive cervical smears (78% vs. 24%). Bivalent IgA appeared to be more sensitive than MIF IgA and showed a stronger correlation with positive cervical smears in obstetric patients (sensitivity 67% vs. 0%, specificity 95% vs. 96%, positive prediction 44% vs. 0%, negative prediction 98% vs. 94%) and with tubal occlusion in sterile women (sensitivity 71% vs. 20%, specificity 87% vs. 94%, positive prediction 84% vs. 77%, negative prediction 76% vs. 55%). MIF IgM was of little diagnostic help. Supplemental to the often difficult C. trachomatis antigen detection, the easily performed Bivalent IgG/IgA appears to be of great value in routine diagnosis of genital chlamydial infections.