MULTICENTER EVALUATION OF A FLUOROMETRIC ENZYME IMMUNOCAPTURE ASSAY TO DETECT TOXOPLASMA-SPECIFIC IMMUNOGLOBULIN-M IN DRIED BLOOD FILTER-PAPER SPECIMENS FROM NEWBORNS

An easy-to-perform fluorometric enzyme immunocapture assay (FEIA) was developed by Labsystems, HeI-sinki, Finland, to detect toxoplasma-spec ific immunoglobulin M (IgM) in dried blood spots, Assay materials were distributed to two sites that have programs in place designed to iden tify infants born with congenital toxoplasma infection: the Statens Se rum Institut, Copenhagen, Denmark, and the New England Regional Newbor n Screening Program, Boston, Mass, Each site tested over 700 dried blo od samples from healthy newborns to define a cutoff at the 99.5 percen tile (5 enzyme immunounits for Copenhagen and 4 enzyme immunounits for Boston), Each site then applied its own cutoff to interpret results f or dried blood spots prepared from either adults with serology suggest ive of acute infection (Copenhagen) or infants determined to be congen itally infected on the basis of serological criteria (Boston), In Cope nhagen, 35 of 38 adult samples were positive by FEIA; the remaining 3 were also negative by immunosorbent agglutination assay for IgM and we re either positive to a small degree or borderline positive for IgA, T hese samples thus may not represent acute infection, In Boston, of 26 congenitally infected infants, 22 were positive by FEIA, The four infa nt specimens not positive by FEIA were either negative or borderline p ositive by the standard Boston assay, These results demonstrate that t he IgM FEIA is a potential alternative to other filter paper assays fo r toxoplasma-specific IgM currently in use for newborns.