Diagnosis of Acute Toxoplasmosis in the First Trimester of Pregnancy by IgG Avidity

The most important concern associated with diagnosing congenital toxoplasmosis is to determine when the mother has been infected. The importance of using serological diagnostic tests such as IgG-avidity assay which can distinguish between recent and past infections has been proven. The present study aimed to diagnose acute toxoplasmosis in the first trimester of pregnancy using IgG-avidity testing.

The present descriptive cross-sectional study was conducted in Hamadan, Iran in 2019. A total of 340 blood samples were collected from pregnant women in the first trimester of pregnancy and stored at -70 °C until experimenting. The IgG antibody titer was then determined. Also, IgM and IgG-avidity titers were measured for those samples with a positive IgG titer.

Out of 340 pregnant women, 106 (31.2%) had a positive and 2 (0.6%) had a suspected IgM test. Of the 106 pregnant mothers with positive IgG, 6 (5.66%) had low IgG-avidity indicating recent infection of toxoplasmosis in the past 3 to 4 months. IgG-avidity titer was moderate in 10 patients (9.43%) and high in 90 patients (84.9%).

Using the IgG-avidity test and its improved methods along with other serological and molecular methods can be effective in determining and differentiating acute toxoplasmosis in pregnant women, especially in the first trimester of pregnancy, and preventing its irreversible complications in the fetus.