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(RIA), highly sensitive laboratory technique used to measure minute amounts of substances including antigens, hormones, and drugs present in the body. The substance or antigen (a foreign substance in the body that causes antibody production) to be measured is injected into an animal, causing it to produce antibodies. Serum containing the antibodies is withdrawn and treated with a radioactive antigen and later with a nonradioactive antigen. Measurements of the amount of radioactivity are then used to determine the amount of antigen present. The technique was developed by Solomon Berson and Rosalyn YalowYalow, Rosalyn Sussman,
1921–2011, American medical physicist, b. New York City, Ph.D. Univ. of Illinois, 1945. As a researcher at the Bronx Veterans Administration Hospital (from 1947), Yalow and colleague Solomon A.
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. Yalow was awarded the 1977 Nobel Prize in Physiology or Medicine for her work.


A general method employing the reaction of antigen with specific antibody, permitting measurement of the concentration of virtually any substance of biologic interest, often with unparalleled sensitivity. The basis of the method is summarized in the competing reactions shown in the illustration. The unknown concentration of the antigenic substance in a sample is obtained by comparing its inhibitory effect on the binding of radioactively labeled antigen to a limited amount of specific antibody with the inhibitory effect of known standards.

Competing reactions that form basis of radioimmunoassay; * indicates the labeled antigen, and † “in known standard solutions or unknown samplesenlarge picture
Competing reactions that form basis of radioimmunoassay; * indicates the labeled antigen, and † “in known standard solutions or unknown samples

A typical radioimmunoassay is performed by the simultaneous preparation of a series of standard and unknown mixtures in test tubes, each containing identical concentrations of labeled antigen and specific antibody. After an appropriate reaction time the antibody- bound (B) and free (F) fractions of the labeled antigen are separated by one of a variety of techniques. The B/F ratios in the standards are plotted as a function of the concentration of unlabeled antigen (standard curve), and the unknown concentration of antigen is determined by comparing the observed B/F ratio with the standard curve.

The radioimmunoassay principle has found wide application in the measurement of a large and diverse group of substances in a variety of problems of clinical and biological interest. It is therefore not unexpected that there are differences in the specific methods employed for the assay of a particular substance. The full potential of the method has yet to be exploited. It seems that virtually any substance of biologic interest can be measured, the method being modified according to the characteristics of the particular substance. See Antibody, Antigen, Immunology


A sensitive method for determining the concentration of an antigenic substance in a sample by comparing its inhibitory effect on the binding of a radioactivity-labeled antigen to a limited amount of a specific antibody with the inhibitory effect of known standards.
References in periodicals archive ?
All of these together comprise and discuss the basic views on the competitive landscape, usage patterns, emerging- and high-growth segments, high-growth regions and countries and their respective regulatory policies, government initiatives, drivers, restraints, and opportunities of the global Radioimmunoassay (RIA) market.
Analysis of each fraction by radioimmunoassay indicated that the most dense lipoprotein fractions, those containing only HDLs, contained the greatest amount (85%) of brevetoxin immunoreactivity within the lipoprotein fractions (Figure 1).
Product Analysis and Development: Detailed insights on upcoming technologies, research and development activities, and new product launches in the Global Radioimmunoassay (RIA) market are provided.
Radioimmunoassay also has its application in the research purposes, and this segment contributed a share of 65.
Open procedures for the award of a three-year supply of generators Radiopharmaceutical Kit Marking Kit for radioimmunoassay - Kit fractionator dose for cell fractionation Pet and radioactive sources for calibration or SEARCH UNIT for the Hospital Riuniti Hospital Villa Sofia Brain, of Palermo see tender documents.
Fyhrquist F, Puutula L: Faster radioimmunoassay of angiotensin I at 37o C.
1] by the aromatase complex was measured in cell supernatants by radioimmunoassay (RIA) as previously described (Nativelle-Serpentini et al.
The radioimmunoassay (RIA) consists of a two-step procedure involving a preliminary extraction and subsequent purification of vitamin D metabolites from serum or EDTA plasma.
Using radioimmunoassay techniques, they measured CRF in nine brain regions using postmortem brain tissue from 13 patients who had died of Alzheimer's and from 13 age- and sex-matched controls with no evidence of such disease.
VA researchers have played key roles in developing the cardiac pacemaker, the CT scan, and radioimmunoassay, among other major medical innovations.
In vitro radioactive reagents for Part 3 pieces fully automated radioimmunoassay system using agents.
Effect of albumin concentration on the assay of serum free thyroxin by equilibrium radioimmunoassay with labeled thyroxin analog (Amerlex Free [T.