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Radioimmunoassay (RIA) is a laboratory technique that measures small concentrations of hormones and antigens in the human body. It involves tagging known antigens with radioactive isotopes and mixing them with antibodies to create a benchmark for testing. The unknown substance is then added, and the amount of antigens is measured by the amount of free radioactive agents. RIA has been used to identify blood volume, iodine metabolism, insulin levels, hepatitis, drug detection, virus monitoring, early detection of leukemia and other cancers, and measurement of human growth hormones. However, it requires special precautions and licenses due to the use of radioactive substances.
Radioimmunoassay, often known simply as RIA in medical circles, is a laboratory method or technique that measures, with relative accuracy, small concentrations of hormones and other antigens in the human body. It is used extensively in a variety of detection screens, from looking for the presence of drugs such as narcotics to scans that seek to identify certain disease or allergy markers. Exactly how this works is somewhat complex and involves “tagging” or labeling known antigens with radioactive isotopes so they can be quickly identified when compared to a sample. In contrast, the actual execution of the test is usually quite straightforward and is typically not as expensive as many of the other procedures involved. However, it requires the use of very sensitive equipment and most hospitals and laboratory facilities require operators to have specialized training and sometimes even a license to perform the tests. The procedure is sometimes considered a bit outdated and has been replaced in places by faster techniques that do not involve the use of radioactive particles. These particles can pose health and safety risks if not handled correctly.
How does it work?
In general, radioimmunoassay is a chemical process that allows researchers to see and identify individual particulates from large groups. The process is complex, but usually not difficult to perform. First, lab technicians must obtain a substance that contains the antigen they are testing. This antigen is then injected with radioactive chemicals, such as an iodine-based gamma-radioactive isotope or some other substance. The radioactive chemicals cause the antigen to become radioactive, which in turn allows it to be observed in certain settings and with certain specialized equipment.
The radioactive antigen is then mixed with a specific amount of antibodies which the scientists have determined are appropriate. Antigens and antibodies bind to each other and become a single substance. This provides the benchmark or basis for testing. Then, an unknown substance that contains a small amount of the antigen is added. This new substance is the substance being tested.
When the new substance, called a “cold” or “unlabeled” substance, is added, the antigens in the new substance try to join the antibodies as well. As they do this, they displace the radioactive substances that were attached to these antibodies. As a result, radioactive substances detach from the antibodies. Scientists can then measure the amount of free radioactive agents that have not been bound to create a binding curve. The binding curve shows the amount of antigens in the unknown substance.
Discovery and first uses
The process was first discovered and perfected in the 1950s by American doctors Rosalyn Yalow and Solomon Berson. It was first used to help researchers identify blood volume, iodine metabolism and insulin levels. Radioimmunoassay has broadened its feasibility by being able to measure trace amounts of substances using sensitive laboratory techniques. Drugs and hormones are some of the substances that the technique can measure today.
More modern applications
Radioimmunoassay is considered the pioneer in nuclear medicine radioactive measurements because radioactive substances generally present themselves with great clarity and precision. The uses of the technique are many and include hepatitis screening from blood banks, drug detection, virus monitoring, early detection of leukemia and other cancers, and measurement of human growth hormones. They can also aid in the detection of many types of ulcers such as peptic ulcers.
While the process is still used in laboratories around the world, in many places it has been replaced in whole or in part by more advanced methods that rely less heavily on radioactive substances. One of the most important of these is the enzyme immunosorbent assay (ELISA), which uses a biochemical process and bypasses the need for radioactivity.
Special precautions and license required
Radioactive substances may be safe when used correctly, but they are quite volatile and must be handled very carefully. Laboratory workers performing this and related procedures usually have to wear special protective clothing when working with particles and typically also have to use specialized machines and equipment. These things can increase the net cost, both of the procedure and of lab operation; some jurisdictions also require technicians to undergo special training for handling radioactive materials. Licenses and certifications may also be required.
