Modification and Evaluation of Avidity IgG Testing for Differentiating of Toxoplasma gondii Infection in Early Stage of Pregnancy

Document Type : Research Article


1 Infection Disease and Tropical Research Center, Immunology Research Center, Faculty of Medicine, Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran

2 Women’s Reproductive Health Research Center, Tabriz University of Medical Sciences, Tabriz, Iran


Toxoplasma gondii infection, an intracellular parasite, is often asymptomatic or is caused by different clinical diseases without being detected. Evaluation of IgG, IgA, and IgM in order to diagnose the pending Toxoplasmosis may confront some problems. Several researches has showned that Toxo IgG avidity can be useful in the recent active Toxoplasmosis. In current study, modification and importance of improved Toxoplasma Avidity IgG testing has been evlauated for differentiating Toxoplasma gondii infection in early stage of pregnancy. Materials and Methods: This experimental study included 300 pregnant women with risk of Toxoplasmosis in their initial months of pregnancy. We randomly divided 300 serum samples into A group (n=60) with high avidity and B group (n=40) with borderline avidity. The samples with Toxo IgG levels were classified to four subgroups. IgG avidity was evaluated by enzyme-linked immunosorbent assay (ELISA) method. Results: The mean absorbance of 100 samples in two groups was calculated, and then, two dilutaion curves with plotted absorbance against dilution were drawn for each serum sample. The results of this study showed that in groups with different concentrations of toxo IgG, appropriate dilution of serum is suitable for testing of Avidity. Our findings revealed the subgroups of 1, 2, 3, and 4 with serum dilutios of 1/3 , 1/6, 1/9, and 1/18 respectively, had real and good avidity. Conclusion: : One of the issues affectig the results of avidity is high concenteration of Toxo IgG in serum sample. As shown in this study, the best points of dilution for well avidity in both high and borderline avidities are marked with arrows in figures 1-8. This study confirmed that improved methods of measuring Toxo Avidity IgG are very important.