Contribution of IgG avidity and PCR for the early diagnosis of toxoplasmosis in pregnant women from the North-Eastern region of Algeria

Background: Acute toxoplasmosis in pregnant women presents a high risk of Toxoplasma transmission to the fetus. Early diagnosis is difficult, especially when serological testing for IgG/IgM antibodies fail to differentiate between a recent and a past infection. In this case, we rely on IgG avidity or PCR assays. Objectives: The aim of this study was to compare conventional ELISA and IgG avidity, with PCR using B1 and P30 primers for the early diagnosis of toxoplasmosis in pregnant women. Methods: Sera were collected from 143 pregnant women and measured by ELISA for anti-Toxoplasma IgG, IgM, IgA and IgG avidity. DNA was extracted from 57 peripheral blood and 14 amniotic fluid samples for PCR amplification. Results: A total of 57 out 143 women were seropositive: 30 (52.6%) were IgG+/IgM-and 27 (43.8%) were IgG+/IgM+; IgA antibodies were positive in 7 (12.2%) cases. IgG avidity was low in 9 women suggesting an acute infection; 3 women presented an intermediate avidity. PCR detected Toxoplasma DNA in 9 women presenting low avidity and was negative for the intermediate avidity cases. Conclusion: PCR combined to avidity IgG performed better than ELISA IgG, IgM and/or IgA assays alone. PCR was useful in the case of intermediate avidity.