Determination of specific immunoglobin G avidity in serodiagnosis of toxoplasmosis

: A total of 37 serum samples from pregnant women were examined for the avidity of toxoplasma IgG antibodies using commercially available enzyme immunoassay (Vidas Toxo IgG Avidity, bio Merieux). Low values of the avidity index were found for 4 samples and borderline ones were found in further 3 cases. Out of 19 serum samples showing the presence of IgG and IgM toxoplasma antibodies, 13 had high avidity index, including 9 samples from women in the first trimester of pregnancy. The results of examinations in these 9 cases allowed to exclude the possibility that toxoplasma infection was acquired during gestation. It is to be concluded that determinations of antitoxoplasma IgG avidity should become routine in every pregnant woman positive in the test for specific IgM antibody.