Newborn screening for congenital Toxoplasma infection: five years experience in Massachusetts, USA

Since 1986, all Massachusetts newborn filter paper blood specimens, and some from New Hampshire, have been screened for the presence of IgM antibodies to Toxoplasma gondii using an enzyme-linked IgM capture assay. Among approximately 530,000 infants screened, 40 had serologically confirmed congenital toxoplasma infection, and 4 additional infants had borderline serologies, for an overall identification and treatment rate of 1:12,000. False positive results from the newborn's filter paper specimen occurred in 22 infants (1/24,000); these were clarified by tests for IgM and IgG in serum specimens obtained 2-3 weeks later from the infant and mother. The screening program would have failed to detect 3 infants with severe infection who were diagnosed on clinical grounds prenatally or at birth and lacked IgM. No infants with a later diagnosis of congenital toxoplasmosis that was missed by screening are known to our statewide network of pediatric infectious disease consultants. Follow-up studies are in progress to evaluate more completely the sensitivity of the IgM assay in newborns and the efficacy of treatment.