Journal of Medical Diagnostic Methods
Open Access

Investigating Radioimmunoassay: The Delicate Science of Trace Antigen Detection

Keenan Kapoor^{* *}Correspondence: Keenan Kapoor, Department of Center Research, University of Wisconsin-Madison, Madison, USA, Email:

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Description

Radioimmunoassay (RIA) is a highly sensitive and specific laboratory technique that has had a transformative impact on medical diagnostics, research, and pharmacology since its development in the 1960s. The method allows the detection and quantification of small concentrations of antigens, such as hormones, drugs, or infectious agents, by utilizing the principle of antigen-antibody interactions combined with radioisotope labeling. While its use has been partially overshadowed by newer techniques such as Enzyme-Linked Immunosorbent Assay (ELISA), RIA remains a vital tool in various fields, particularly in endocrinology and clinical diagnostics. RIA was developed in 1960 by Dr. Solomon Berson and Dr. Rosalyn Yalow, two American scientists, who received the Nobel Prize in Physiology or Medicine in 1977 for their pioneering work. The key breakthrough that led to the invention of RIA was the ability to use radioactive isotopes as labels for antigens or antibodies. Their approach combined immunological principles of specific antigen-antibody interactions with the highly sensitive detection capabilities of radiation. This allowed the measurement of very low concentrations of substances in biological samples, such as blood or urine, which had previously been difficult to detect. Both antigens compete for a limited number of antibody binding sites, and the amount of radioactivity in the bound antigen is inversely proportional to the concentration of the unlabeled antigen in the sample. After the antigens have bound to the antibody, the bound and free fractions are separated. The radioactivity of the bound fraction is measured, and from this, the concentration of the unknown antigen can be determined by comparison to a standard curve created with known concentrations of the radiolabeled antigen. The first step in RIA is to produce or obtain a specific antibody that can recognize and bind to the antigen of interest. The radiolabel is attached to the antigen molecule without altering its ability to bind to the antibody. The sample containing the unknown concentration of the antigen is mixed with the radiolabeled antigen and the specific antibody. Both the labeled and unlabeled antigens compete for the antibody binding sites. The more antigen present in the sample, the less labeled antigen will bind to the antibody. After a period of incubation, the bound antigenantibody complex is separated from the unbound radiolabelled antigen. This can be done using techniques like precipitation, centrifugation, or chromatography. The radioactivity of the bound fraction is measured using a gamma counter or scintillation counter. The amount of bound radioactivity is inversely related to the concentration of the antigen in the sample. The amount of antigen in the sample is determined by comparing the radioactivity measurement to a standard curve. This curve is prepared by using known concentrations of radiolabelled antigen, and the radioactivity is plotted against the antigen concentration. RIA has been instrumental in advancing many areas of medical science and research, particularly in the diagnosis of diseases, monitoring of drug levels, and understanding of physiological processes. The use of radioactive isotopes raises concerns regarding safety and disposal of radioactive waste. Strict protocols are required to ensure safety during handling and disposal. Radioimmunoassay remains a crucial technique in various scientific and clinical disciplines, despite the rise of newer immunoassay methods. Its high sensitivity and specificity make it invaluable for detecting trace amounts of hormones, drugs, and disease markers, contributing to better diagnosis, treatment, and understanding of a wide range of medical conditions.