DHT, RIA, 100 tests

The procedure follows the basic principle of radioimmunoassay where there is competition between the radioactive and non-radioactive antigen for a fixed number of antibody binding sites.

The amount of (I-125)-labeled analyte bound to the antibody is inversely proportional to the concentration of unlabeled analyte present.

The separation of free and bound antigen is achieved by using a double antibody system.