Seasonal influence on TORCH infection and analysis of multi-positive samples with indirect immunofluorescence assay

Background TORCH including the pathogens of Toxoplasma gondii (TOX), rubella virus (RV), cytomegalovirus (CMV), and herpes simplex virus (HSV) causes intrauterine infections and poses a worldwide threat to women especially in pregnancy. In this study, we described the seasonal difference in TORCH infection and analyzed the anti-TORCH IgM multipositive serum samples by the indirect immunofluorescence assays (IFA). Methods To observe the seasonal influence of the anti-TORCH IgG and IgM antibodies, a retrospective study was conducted with 10 669 women (20-40 y old) before pregnancy from August 2016 to July 2017. Totally 199 ELISA anti-TORCH IgM multipositive serum samples were further tested by IFAs for false-positive analysis. Results The prevalence of positive HSV1-IgM, RV-IgM, HSV2-IgM, CMV-IgM, and TOX-IgM in the present population was 6.30%, 2.55%, 1.94%, 1.24%, and 0.67%, respectively. Additionally, the prevalence of positive RV-IgM, CMV-IgM, and HSV1-IgM was statistically different among four seasons, with the highest positive rates of RV-IgM (4.12%) in autumn, CMV-IgM (1.75%) in summer, and HSV1-IgM (7.53%) in winter. The confirmatory IFAs showed that the positive rates of RUV-IgM, CMV-IgM, and HSV2-IgM were significantly different from those in ELISA screening experiments. Interestingly, only 32.7% (65/199) of the TORCH IgM multipositive results were consistent with those by the IFA, indicating that cross-reaction caused false positives were common in ELISA IgM antibody screening. Conclusion The TORCH infection displayed different prevalence among four seasons in our 12-month retrospective study. The IgM multipositives by ELISA screening may need further confirmation analysis due to its relatively high cross-reaction rate.