Enzyme immunoassay of hepatitis associated antigen (HAA)

Due to its high sensitivity, radioimmunoassay has become of great importance in the detection and measurement of levels of proteins and steroids in body fluids. However, this method involves the use of expensive equipment and radioactive material. Herein is described an alternate method to radioimmunoassay, which uses an enzyme-labeled rather than a radioactively-labeled antibody. An enzyme immunoassay procedure, the Cordia HAA-enzyme Immunoassay, for the detection of hepatitis-associated antigen has been evaluated. With this technique a sandwich type immunoassay with an alkaline phosphatase tagged second antibody is used. The presence of antigen is detected by the p-nitrophenyl phosphotase activity of the bound enzyme. In 1083 clinical samples from patients of Jackson Memorial Hospital, only 19 discrepant results were found when tested by both the Cordia and the Ausria II methods. Eight had sufficient sera for retesting, yielding two positive Cordia, negative Austia; one negative Cordia, positive Ausria; one borderline positive; and four unconfirmed false positives by Cordia.