This assay employs the competitive inhibition enzyme immunoassay technique. The microtiter plate provided in this kit has been pre-coated with goat-anti-rabbit antibody. Standards or samples are added to the appropriate microtiter plate wells with an antibody specific for E2 and Horseradish Peroxidase (HRP) conjugated E2. The competitive inhibition reaction is launched between with HRP labeled E2 and unlabeled E2 with the antibody. A substrate solution is added to the wells and the color develop