Serum IgM to Chlamydia trachomatis in pregnancy: its usefulness for screening

Asymptomatic infection with Chlamydia trachomatis represents an important health problem. A non-invasive diagnostic test to screen pregnant women is needed that is cost effective and can be used widely, especially in developing countries. In this setting, quantitation of antichlamydial IgM antibodies may offer an additional strategy for the control of C. trachomatis infection. The aim of this prospective study is to evaluate the quantitation of serum antichlamydial IgM antibodies, based on absorbance (A) values, in pregnant women for the prediction of C. trachomatis infection. Serum samples from a cohort of 148 pregnant women (first to third trimesters; age range: 18-35 years) presenting to the antenatal department at Safdarjang Hospital were tested for IgM antibodies specific to C. trachomatis by an enzyme-linked immunosorbent assay (ELISA) kit (Novum Diagnostics, Germany). Co-infection with other STD pathogens was ruled out. In this cohort, 85 (57.4%) pregnant women were found to be positive for IgM antibodies to C. trachomatis. Based on the cut-off value of the ELISA test (calculated as 0.558), pregnant women with an A value between 0.558 and 0.999 and those with a value > 1.000 were categorised as low positive (LP, n=41) and high positive (HP, n=44), respectively. The differences in mean A values for the LP versus negative groups (0.7504 versus 0.2249, P<0.05) and the HP versus negative groups (1.5353 versus 0.2249, P<0.05) were statistically significant. Maximum seroprevalence (44.4%, P<0.05) was found among those in the HP group in the first trimester of pregnancy. Multigravidae (34.4%, P<0.5) and multiparous (34.9%, P<0.5) pregnant women in the HP group were at an increased risk of chlamydial infection. As overall results indicated that pregnant women in the HP group were at higher risk, we stress the importance of large-scale screening of pregnant women for C. trachomatis infection, particularly in developing countries where sophisticated techniques for collection/diagnosis are as yet unavailable.