In this assay the Alpha 1 Acid Glycoprotein / AGP present in samples reacts with the anti-Alpha 1 Acid Glycoprotein / AGP antibodies which have been adsorbed to the surface of polystyrene microtitre wells. After the removal of unbound proteins by washing, anti-Alpha 1 Acid Glycoprotein / AGP antibodies conjugated with horseradish peroxidase (HRP), are added. These enzyme-labeled antibodies form complexes with the previously bound Alpha 1 Acid Glycoprotein / AGP. Following another washing step, the enzyme bound to the immunosorbent is assayed by the addition of a chromogenic substrate, 3,3’,5,5’-tetramethylbenzidine (TMB). The quantity of bound enzyme varies directly with the concentration of Alpha 1 Acid Glycoprotein / AGP in the sample tested; thus, the absorbance, at 450 nm, is a measure of the concentration of Alpha 1 Acid Glycoprotein / AGP in the test sample. The quantity of Alpha 1 Acid Glycoprotein / AGP in the test sample can be interpolated from the standard curve constructed from the standards, and corrected for sample dilution.

Alpha 1 Acid Glycoprotein / AGP is a 52 kDa serine protease inhibitor (serpin) in blood, which protects tissue from enzymes from inflammatory cells, especially elastase. In certain acute phase inflammatory reactions, Alpha 1 Acid Glycoprotein / AGP is elevated in order to limit the damage caused by activated neutrophil granulocytes and their enzyme elastase. Disorders of Alpha 1 Acid Glycoprotein / AGP include Alpha 1 Acid Glycoprotein / AGP deficiency, a hereditary disorder that can lead to severe tissue breakdown during inflammation. This may result in pulmonary emphysema and liver cirrhosis, in severe cases genetic variants of Alpha 1 Acid Glycoprotein / AGP do occur.