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.