Performance of a Western blot assay to compare mother and newborn anti-toxoplasma antibodies for the early neonatal diagnosis of congenital toxoplasmosis

The aim of this study was to retrospectively evaluate the performance of a Western blot assay to compare mother and newborn anti-Toxoplasma gondii ant ibodies for the early neonatal diagnosis of congenital toxoplasmosis. Since specific anti-Toxoplasma IgM or IgA is detected inconstantly at birth in t he neonate, the diagnosis of congenital toxoplasmosis is often delayed unti l 6-9 months, after IgG titers have been observed persistently. In this stu dy, 81 pail-ed samples from GO mother/child pairs were tested for IgG and I gM patterns. All mothers had (or were strongly suspected to have) acquired toxoplasmosis during pregnancy. Specific IgM and IgA were simultaneously de tected by immunocapture tests, and IgG was titrated. A serological and clin ical follow-up of infants was conducted during the first year of life until the diagnosis of congenital toxoplasmosis could be either confirmed or rul ed out. Seventeen of the 60 newborns were congenitally infected. Specific I gM or IgA was detected by immunocapture at birth in 76.5% and 70.6% of cord sera from infected neonates, respectively, with an equal specificity of 77 .5%. Comparative Western blot allowed the detection of neosynthesized IgG a nti IgM in the cord blood of 50% and 78.6% of infected infants, respectivel y, with a specificity of 100%. The combination of IgA and IgM immunocapture tests, the analysis of IgG and IgM Western blot patterns, and the combinat ion of both techniques allowed the detection of 94%, 93%, and 100% of cases within the first 3 months of life, respectively. In conclusion, Western bl otting seems to be a useful complementary tool for the early postnatal diag nosis of congenital toxoplasmosis.