T3 total is a one-step immunoasay to determine the presence of total triiodothyronine (total T3) in human serum using competitive micro plate enzymeimmunoassay. Platesare coated with anti-T3 antibodies.Serum reference, patient specimens or control serum is first added tomicroplate well. Enzyme-T3 conjugate is added. A competition reaction results between the enzyme-triiodothyronine conjugate and a serum containing the nativetotal triiodothyronine for a limited number of antibody combining sitesimmobilized on the well. Unbound conjugate is removed by washing. The enzyme activity in the antibody-bound fraction is inversely proportional to the native total triiodothyronine concentration. Theenzyme activity is revealed by a color change in TMB-substrate solution.