This assay employs the competitive inhibition enzyme immunoassay technique. A monoclonal antibody specific to the index has been pre-coated onto a microplate. A competitive inhibition reaction is launched between biotin labeled the index and unlabeled the index (Standards or samples) with the pre-coated antibody specific to the index. After incubation the unbound conjugate is washed off. Next, Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. The amount of bound HRP conjugate is reverse proportional to the concentration of the index in the sample. After addition of the substrate solution, the intensity of color developed is reverse proportional to the concentration of the index in the sample.