Radioimmunoassay (RIA)

The technique of radioimmunoassay has revolutionized research and clinical practice in many areas, e.g.,

The technique was introduced in 1960 by Berson and Yalow as an assay for the concentration of insulin in plasma. It represented the first time that hormone levels in the blood could be detected by an in vitro assay.

The Technique

Separating Bound from Free Antigen

There are several ways of doing this.

Radioimmunoassay is widely-used because of its great sensitivity. Using antibodies of high affinity (K0 = 108–1011 M−1), it is possible to detect a few picograms (10−12 g) of antigen in the tube.
[Link to page that discusses antibody affinity]

The greater the specificity of the antiserum, the greater the specificity of the assay.

Link to an illustration of antibody specificity demonstrated by radioimmunoassay.

The main drawbacks to radioimmunoassay are the expense and hazards of preparing and handling the radioactive antigen.

The enzyme-linked immunosorbent assay (ELISA) has many of the advantages (e.g., sensitivity, ease of handling multiple samples) without the disadvantages of dealing with radioactivity. Link to a description of ELISA

Despite these drawbacks, RIA has become a major tool in the clinical laboratory where it is used to assay

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9 March 2011