Antibodies to Toxoplasma gondii in eluates from filter paper blood specimens.

Blood and serum samples were tested directly for antibodies to Toxoplasma gondii, or as eluates from filter paper using the dye test, IgM enzyme-linked immunosorbent assay (ELISA) and IgM immunosorbent agglutination assay (ISAGA). The specificity and reproducibility of all three assays based on filter paper eluate was satisfactory. The sensitivity of testing eluates was 10 IU by the dye test and 53 EIU by IgM ELISA. IgM ISAGA findings, using eluate or sera, were comparable. Seroprevalence studies of congenital toxoplasmosis can be based on IgM measurement by ISAGA using eluates of filter paper stored infants' blood. Dye test and IgM ISAGA testing of eluate can be used to reduce the frequency of venepuncture when investigating infants for suspected congenital toxoplasmosis.