This assay employs a two-site sandwich ELISA to quantitate ENG in samples. An antibody specific for ENG has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and anyENG present is bound by the immobilized antibody. After removing any unbound substances, a biotin-conjugated antibody specific for ENG 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-enzym