Seroprevalence of Toxoplasma gondii, Rubella virus and Cytomegalovirus among pregnant women and the importance of avidity assays

Objectives: To determine the seroprevalence of Toxoplasma gondii (T. gondii), Rubella virus, and Cytomegalovirus (CMV) among pregnant women in Izmir, Turkey. Methods: Medical records of pregnant women attending Izmir Tepecik Training and Research Hospital, Izmir, Turkey between January 2014 and January 2016 were analyzed in this retrospective cross-sectional study. The 7513 T. gondii IgM/IgG results, 7189 Rubella IgM/IgG results, 906 CMV IgM/IgG results and 146 avidity test results were evaluated. Specific IgM and IgG antibodies were detected by an automated chemiluminescent enzyme immunoassay method. Immunoglobulin G avidity tests were performed using a multiparametric immunoassay system. Results: The rates of IgG positivity for T. gondii was 32.3%, Rubella virus 93.5%, and CMV 98.9%. Immunoglobulin M antibodies were found to be positive in 138 (1.9%) cases for T. gondii, 88 (1.2%) cases for Rubella, and 14 (1.5%) cases for CMV. Avidity tests were ordered from 146 of 218 patients who were found both IgM and IgG positive. Among 146 patients, 6 patients had a low avidity index (all for T. gondii), 11 patients showed borderline avidity, and 129 patients revealed high avidity. Conclusion: In our region, whereas the rates of IgG positivity for Rubella and CMV are high, most pregnant women were susceptible to T. gondii infections. In order to enhance the reliability of the serological diagnosis, avidity tests should be performed in all IgM positivities detected together with IgG positivity