Lack of value of specific IgA detection in the postnatal diagnosis of congenital toxoplasmosis

To improve the performance of the postnatal diagnosis of congenital toxopla smosis, we assessed the detection of IgA antibodies to Toxoplasma gondii by ELISA, compared with that of IgM by ELISA, ISAGA, and IFAT and neosynthesi zed antibodies using Western blot. From 1993 to 1996, IgA antibodies were d etected using the Toro IgA test (SFRI, Societe Francaise de Recherches et d 'Investissements, Bordeaux, France), in 195 serum and cord blood samples fr om 63 infants born to mothers who seroconverted during pregnancy. Eighteen infants had proven congenital toxoplasmosis (confirmed by the presence of I gG after 12 months of life) and 45 had no congenital toxoplasmosis (negativ ity 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, whic h 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 co rd blood) and Western blot (83.3% on sera, 72.7% on cord blood). IgA antibo dies were never detected by ELISA earlier than IgM or neosynthesized Ig (an tibodies synthesized by infants). Thus, the detection of IgA antibodies by Toro IgA is; not useful in improving the diagnosis of congenital toxoplasmo sis. (C) 1999 Wiley-Liss, Inc.