To improve the performance of the postnatal diagnosis of
congenital toxoplasmosis, we assessed the detection of
IgA antibodies to Toxoplasma gondii by ELISA, compared with that of
IgM by ELISA, ISAGA, and IFAT and neosynthesized
antibodies using Western blot. From 1993 to 1996,
IgA antibodies were detected using the Toxo
IgA test (SFRI, Société Française de Recherches et d'Investissements, Bordeaux, France), in 195 serum and cord blood samples from 63 infants born to mothers who seroconverted during pregnancy. Eighteen infants had proven
congenital toxoplasmosis (confirmed by the presence of
IgG after 12 months of life) and 45 had no
congenital toxoplasmosis (negativity of
IgG after 6-12 months of life). The sensitivity of
IgA detection by ELISA on serum and cord blood samples was 38.9 and 54.5% respectively, which is low when compared with the sensitivity of
IgM detection by ISAGA (66.7% on serum samples, 90.9% on cord blood), ELISA (61.1% on sera, 81.8% on cord blood) and Western blot (83.3% on sera, 72.7% on cord blood).
IgA antibodies were never detected by ELISA earlier than
IgM or neosynthesized Ig (
antibodies synthesized by infants). Thus, the detection of
IgA antibodies by Toxo
IgA is not useful in improving the diagnosis of
congenital toxoplasmosis.