Strategy for diagnosis of congenital toxoplasmosis: Evaluation of methods comparing mothers and newborns and standard methods for postnatal detectionof immunoglobulin G, M, and A antibodies

In a study involving 14 laboratories supported by the European Community Bi omed 2 program, we evaluated immunologic methods for the postnatal diagnosi s of congenital toxoplasmosis (CT). Among babies born to mothers who seroco nverted to positivity for toxoplasmosis during pregnancy, we analyzed 55 ba bies with CT on the basis of persistent anti-Toxoplasma immunoglobulin G (I gG) at 1 year of life and 50 control babies without anti-Toxoplasma IgG at 1 year of life in the absence of curative treatment,vith pyrimethamine-sulf onamides. We tested in-house methods such as the enzyme-linked immunofiltra tion assay (ELIFA) or Immunoblotting (IB) for the detection of IgG pr IgM; these methods allowed comparison of the immunologic profiles of the mothers and the infants. We compared ELIFA and IB with a commercial enzyme immunoa ssay (EIA) or in-house immunosorbent agglutination assay (ISAGA) for the de tection of IgM or IgA. The performances of combinations of methods were als o assessed. A cumulative sensitivity of 98% during a 1-year follow-up was o btained with the ELIFA plus ISAGA combination. Only one case of CT was miss ed by the ELIFA plus ISAGA combination, whereas three cases were missed by the IB plus ISAGA combination, even though 48% of patients with CT were tre ated with pyrimethamine-sulfonamides, which are known to inhibit antibody n eosynthesis. A similar performance was obtained with either ELIFA or IB in combination with EIA. The difference in performance between ELIFA plus ISAG A and TB plus ISAGA was not statistically significant (P = 0.31), and we co nclude that both combinations of tests can be used for the diagnosis of CT in newborns.