The Effect of Toxoplasmosis on Pregnant Women and Its Diagnosis by “VIDAS Test of IgG Avidity”

Abstract

Toxoplasmosis is well known as a cause of infection in pregnant women. Although many serological methods are available, diagnosis of early Toxoplasmosis may be extremely difficult. Toxoplasmosis is typically diagnosed during pregnancy via testing of maternal serum for IgM and IgG anti-Toxoplasma antibodies. Toxoplasmosis is normally asymptomatic, but it can have serious effects in immune-deficient individuals. Because avidity increases over time during infection, determining specific IgG avidity allows for more precise dating. Long-term IgM persistence makes it difficult to distinguish between acute and chronic infection. Seventy-six women were tested for VIDAS lgM, lgG antibodies, and VIDAS toxo-IgG avidity during the first 16 weeks of pregnancy. Low avidity antibodies were found in two (33.3%) of the six IgM-positive sera and four (11.11%) of the IgG-positive sera. Low avidity was noticed in 2 (3.27%) of the 61 sera that were negative for IgM. The low avidity indicates a recent infection, whereas high avidity in 4 (50%) of the 6 positive IgM and 24 (74.74%) of the 33 positive IgG indicates a long-ago infection. These conclusions emphasise the importance of using “VIDAS IgG avidity” in conjunction with the VIDAS IgM and IgG assays to offer to prove the presence of acute infection from a single serum sample for pregnant women.