How to estimate time of infection with Toxoplasma gondii in pregnant women. Use of specific IgG and IgM kinetics by 7 techniques on 691 sera.

A difficulty when detecting both anti-Toxoplasma gondii-specific IgG and IgM in pregnant women is estimating the date of infection. The aim of this study was to compare the anti-Toxoplasma-specific immunoglobulin kinetics of 7 serological techniques to date the infection and to draw kinetic curves that are easy to use on a daily basis. IgG and IgM antibodies were measured on 691 sera samples. IgM appeared a few days, less than 1 week, after the beginning of the infection. Then, the levels of IgM reached a peak at approximately 3, 4, and 5 weeks with Toxo-ISAGA® IgM, IgM homemade indirect immunofluorescence assays, and Vidas Toxo® IgM, respectively. Furthermore, the Architect Toxo® IgG titers were higher than those of the Vidas Toxo® IgG results in recent infection (less than 6 months). This study provides new average IgM and IgG curves that can help to determine the approximate date of infection.