Neonatal screening for congenital toxoplasmosis in the Poznan region of Poland by analysis of Toxoplasma gondii-specific IgM antibodies eluted from filter paper blood spots

Objectives. The aims of the study were to determine the prevalence of conge nital toxoplasmosis at birth in the Poznan region of poland, the value of t he serologic examination of filter paper blood specimens collected from new borns for the diagnosis of congenital Toxoplasma infection and the duration of anti-Toxoplasma-specific IgM antibodies in infants' sera. Materials and methods. All neonates born in the maternity wards of the Univ ersity Hospital of Gynaecology and Obstetrics in Poznan and in 10 selected obstetrics wards in the district hospitals were included. Blood samples wer e collected on filter paper cards, between the first and sixth day of life, screened for anti-Toxoplasma-specific IgM antibodies by an immunocapture e nzyme-linked immunosorbent assay and if positive further analyzed for speci fic IgG and IgA antibodies. Results. Between June, 1996, and October, 1998, filter paper samples from 2 7 516 liveborn infants were tested, which constituted similar to 75% of all births and 83% of liveborn neonates from the Poznan region. Anti-T. gondii -specific IgM antibodies were found in 13 newborns, equivalent to a prevale nce of Toxoplasma-specific IgM in newborns of 1 per 2117 liveborn children (0.47 per 1000) or 1 per 870 children (1.15 per 1000) born to seronegative women at risk of primary T. gondii infection during pregnancy. We identifie d two congenitally infected infants who were IgM-negative at birth, had a c lassic triad of clinical symptoms during the first year of life and had hig h levels of specific IgG, The birth prevalence of congenital toxoplasmosis in the Poznan region was at least 1 per 1834 live births (0.55 per 1000) or 1 per 754 live neonates born to seronegative women (1.33 per 1000). The se nsitivity of the IgM assay on eluate from filter paper was not more than 86 .7%, and the mean duration of IgM detectable by enzyme-linked immunosorbent assay in serum samples was the first 4.8 weeks of life. Conclusion. In Poland the screening for congenital toxoplasmosis detecting one case per each 2000 live births could be considered for inclusion in exi sting national neonatal screening programs for phenylketonuria and congenit al hypothyroidism.