IMPROVED DIAGNOSIS OF PRIMARY TOXOPLASMA-GONDII INFECTION IN EARLY-PREGNANCY BY DETERMINATION OF ANTITOXOPLASMA IMMUNOGLOBULIN-G AVIDITY

The ability to discriminate between primary Toxoplasma gondii infectio n acquired in early pregnancy and infection that occurred prior to pre gnancy was assessed by an enzyme immunoassay (EIA) to determine tile a vidity of toxoplasma-specific immunoglobulin G (IgG), The results were compared to those of the Platelia Toxo-IgM EIA and the dye test, The mean IgG avidity of 73 serum samples collected within 20 weeks after t he estimated time of infection was 5.9%, Among 26 serum samples showin g latent infection (toxoplasma-specific IgG positive and IgM negative) and 56 IgM-positive serum samples with a low dye test titer (<300 IU/ ml), the mean avidities were 51,3 and 57.5%, respectively. A total of 72,8% of 92 IgM-positive serum samples with a high dye test titer (>30 0 IU/ml), suggesting a recent toxoplasma infection, had an IgG avidity of >20%, indicating that the infection started more than 20 weeks ear lier. By introducing high IgG avidity as a criterion in the first half of pregnancy to exclude the possibility that toxoplasma infection was acquired during gestation, many women will avoid unnecessary Examinat ions, treatment, and anxiety.