This assay employs the competitive inhibition enzyme immunoassay technique. A monoclonal antibody specific to Cholecystokinin (CCK) has been pre-coated onto a microplate. A competitive inhibition reaction is launched between biotin labeled Cholecystokinin (CCK) and unlabeled Cholecystokinin (CCK) (Standards or samples) with the pre-coated antibody specific to Cholecystokinin (CCK). After incubation the unbound conjugate is washed off. Next, avidin conjugated to Horseradish Peroxidase (HRP) is ad