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Radioimmunoassay
 
 
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Radioimmunoassay (RIA) is a scientific method
Scientific method

Scientific method refers to techniques for investigating phenomenon, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and Measure evidence subject to specific principles of reasoning....
 used to test antigen
Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
s (for example, hormone
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
 levels in the blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
) without the need to use a bioassay
Bioassay

Bioassay is a shorthand commonly used term for biological assay and is a type of scientific experiment. Bioassays are essential in the development of new drugs, and monitoring pollutants in the environment....
. It was developed by Rosalyn Yalow and Solomon Aaron Berson
Solomon Berson

Solomon Aaron Berson was an United States physician and scientist whose discoveries, mostly together with Rosalyn Sussman Yalow, caused major advances in clinical biochemistry....
 in the 1950s. In 1977, Rosalyn Sussman Yalow
Rosalyn Sussman Yalow

Rosalyn Sussman Yalow is an United States medicine physics, and a co-winner of the 1977 Nobel Prize in Physiology or Medicine for her development of the radioimmunoassay technique....
 received the Nobel Prize in Medicine for the development of the RIA for insulin: the precise measurement of minute amounts of such a hormone
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
 was considered a breakthrough in endocrinology
Endocrinology

Endocrinology is a branch of medicine dealing with disorder of the endocrine system and its specific secretions called hormones....
.

Although the RIA technique is extremely sensitive and extremely specific, it requires a sophisticated apparatus and is costly.






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Radioimmunoassay (RIA) is a scientific method
Scientific method

Scientific method refers to techniques for investigating phenomenon, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and Measure evidence subject to specific principles of reasoning....
 used to test antigen
Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
s (for example, hormone
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
 levels in the blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
) without the need to use a bioassay
Bioassay

Bioassay is a shorthand commonly used term for biological assay and is a type of scientific experiment. Bioassays are essential in the development of new drugs, and monitoring pollutants in the environment....
. It was developed by Rosalyn Yalow and Solomon Aaron Berson
Solomon Berson

Solomon Aaron Berson was an United States physician and scientist whose discoveries, mostly together with Rosalyn Sussman Yalow, caused major advances in clinical biochemistry....
 in the 1950s. In 1977, Rosalyn Sussman Yalow
Rosalyn Sussman Yalow

Rosalyn Sussman Yalow is an United States medicine physics, and a co-winner of the 1977 Nobel Prize in Physiology or Medicine for her development of the radioimmunoassay technique....
 received the Nobel Prize in Medicine for the development of the RIA for insulin: the precise measurement of minute amounts of such a hormone
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
 was considered a breakthrough in endocrinology
Endocrinology

Endocrinology is a branch of medicine dealing with disorder of the endocrine system and its specific secretions called hormones....
.

Although the RIA technique is extremely sensitive and extremely specific, it requires a sophisticated apparatus and is costly. It also requires special precautions, since radioactive substances are used. Therefore, today it has been largely supplanted by the ELISA
ELISA

Enzyme-Linked ImmunoSorbent Assay, also called ELISA, Enzyme ImmunoAssay or EIA, is a biochemistry technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample....
 method, where the antigen-antibody reaction is measured using colorometric
Colorimetry

Colorimetrycan refer to:* the quantitative study of color perception. It is similar to spectrophotometry, but may be distinguished by its interest in reducing spectra to tristimulus values, from which the perception of color derives....
 signals instead of a radioactive signal.

To perform a radioimmunoassay, a known quantity of an antigen
Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
 is made radioactive, frequently by labeling it with gamma-radioactive isotope
Isotope

Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
s of iodine
Iodine

Iodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
 attached to tyrosine
Tyrosine

Tyrosine or 4-hydroxyphenylalanine, is one of the 20 amino acids that are used by cell to protein biosynthesis proteins. This is a non-essential amino acid and it is found in casein....
. This radiolabeled antigen is then mixed with a known amount of antibody for that antigen, and as a result, the two chemically bind to one another. Then, a sample of serum
Serum

Serum may refer to:*Blood plasma, with clotting factors removed*Antiserum, for transfer of passive immunity*Serous fluid, any clear bodily fluid...
 from a patient containing an unknown quantity of that same antigen is added. This causes the unlabeled (or "cold") antigen from the serum to compete with the radiolabeled antigen for antibody binding sites.

As the concentration
Concentration

In chemistry, concentration is the measure of how much of a given chemical substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions, where it refers to the amount of solute in the solvent....
 of "cold" antigen is increased, more of it binds to the antibody, displacing the radiolabeled variant, and reducing the ratio of antibody-bound radiolabeled antigen to free radiolabeled antigen. The bound antigens are then separated from the unbound ones, and the radioactivity of the free antigen remaining in the supernatant is measured. A binding curve can then be plotted, and the exact amount of antigen in the patient's serum can be determined.

With this technique, separating bound from unbound antigen is crucial. Initially, the method of separation employed was the use of a second "anti-antibody" directed against the first for precipitation and centrifugation. The use of charcoal suspension for precipitation was extended but replaced later by Drs. Werner and Acebedo at Columbia University for RIA of T3 and T4. An ultramicro RIA for human TSH was published in BBRC (1975) by Drs. Acebedo, Hayek et al.

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