Principles and applications of radioimmunoassay RIA

RIA is one of the primary techniques which has historically been important for clinical knowledge and testing for hormones. Indeed, RIA was first developed by Yalow and Berson to measure the circulating levels of the important hormone insulin. However, since this early description of the technique, very many similar assays have appeared for hundreds of substances differing markedly in chemical structure and biological activity. 

As noted earlier, RIA typically depends on the use of radiolabelled antigens, and in the case of the first report in the scientific literature the antigen in question was insulin. This classic radioimmunoassay for insulin will be used as the fundamental example of how this technique operates in practice. 

RIA relies on the basic principles of antigen-antibody complex formation outlined earlier in the chapter. 

Step 1- Incubate antibody with labelled antigen Limiting and constant amount of antibody (Ab) 

Incubated with a constant amount of radioactively labelled antigen (Ag ) 

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