Double antibody immunoradiometric assay of hGH employing a terminal labeling technique.

A method is described, and validated for hGH, using a double antibody immunoradiometric assay and a universal antibody coupled to a chelating moiety that can be labeled as the terminal step in the assay procedure. This technique, usable for any antigen, precludes the need for radiolabeled specific antibodies, and because of the short-lived radionuclide used in the terminal labeling step, generates no radioactive waste. The assay itself uses a specific first antibody coupled to a solid support (paper disc) to which the antigen binds. A specific second antibody from a second species is then attached to the solid phase retained antigen. Now a third antibody is attached, which has been generated from a third species against the second antibody acting as an antigen, and which carries transferrin as a chelating moiety. This final complex is labeled with 113mIn and the plot of the percentage of the total activity bound against the hGH concentration provides the derived values for the antigen levels present in the assay solution.