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.