Immunometric Assays

Immunometric assays, also known as sandwich assays, use two antibodies specific to the antigen to capture or “sandwich” antigen in the well for detection. Immunometric assays exhibit a direct correlation between antigen concentration and substrate response. Immunometric assays typically employ a “capture” antibody coated on the plate to bind the antigen of interest. During a second incubation, the antigen is bound by a second “detection” antibody that is also specific to the antigen. The detection antibody can either be bound by a secondary antibody-enzyme conjugate, or the detection antibody itself is enzyme-conjugated. When chromogenic substrate is added to the assay to develop color, samples with high antigen concentration generate more signal than those with low antigen concentration, producing a signal directly proportional to the amount of antigen in the sample. This correlation can then be used to extrapolate the concentration of antigen in an unknown sample from a standard curve.