Diagnosis of Congenital Toxoplasmosis: No Benefit of IgA Antibody Detection by Platelia ELISA in a Tricentric Evaluation

The diagnostic accuracy of a commercial Toxoplasma gondii IgA antibody enzyme-linked immunosorbent assay (ELISA) was evaluated in the context of routine practice on 289 newborns with congenital toxoplasmosis (CT) and 220 healthy controls. The performance of this assay was compared to that of the current gold-standard test for anti-Toxoplasma IgM detection, an immunosorbent agglutination assay (ISAGA). IgM and IgA sensitivity and specificity were assessed in cord and postnatal samples. The sensitivity of IgA detection by ELISA on all serum and peripheral blood samples was 60.56% and 56.52%, respectively, which is low compared with the sensitivity of IgM detection by ISAGA (73.26% on serum samples, 82.35% on peripheral blood). Adding the T. gondii IgA antibody ELISA to the diagnostic panel did not significantly increase the overall performance of the serological diagnosis based on IgM detection.