The radioimmunoassay format is inherently associated with a high analytical sensitivity and in combination with a specific detection antiserum, result in a high performing assay.
Radioimmunoassays are based on high sensitivity in vitro assay techniques to measure concentrations of antigens by the use of antibodies or alternatively to detect antibodies for a specific antigen. The assays measure the presence of an antigen with very high sensitivity. The target antigen is labeled radioactively and bound to its specific antibodies.
A blood-serum is added to initiate a competitive reaction of the labeled antigens from the preparation, and the unlabeled antigens from the serum-sample, with the specific antibodies. The competition for the antibodies will release a certain amount of labeled antigen. This amount is proportional to the ratio of labeled to unlabeled antigen.
The concentration of unlabeled antigen is increased, more of it binds to the antibody, displacing the labeled variant. The bound antigens are then separated from the unbound ones, and the radioactivity of the free antigens remaining in the supernatant is measured.
Radioimmunoassay is an old assay technique, but it is still a widely used assay and continues to offer distinct advantages in terms of simplicity and sensitivity. Their simplicity and excellent performance results in stable and repeatable assays.