This assay employs a two-site sandwich ELISA to quantitate IgM in samples. An antibody specific for IgM has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any IgM present is bound by the immobilized antibody. After removing any unbound substances, a biotin-conjugated antibody specific for IgM is added to the wells. After washing, Streptavidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of IgM bound in the initial step. The color development is stopped and the intensity of the color is measured.