Defination:-
A procedure that measures minute amounts of a substance, such as a hormone or drug, by quantitating the binding, or the inhibition of binding, of a radiolabeled substance to an antibody.
Radioimmunoassay (RIA) is a sensitive method for measuring very small amounts of a substance in the blood. Radioactive versions of a substance, or isotopes of the substance, are mixed with antibodies and inserted in a sample of the patient's blood. The same non-radioactive substance in the blood takes the place of the isotope in the antibodies, thus leaving the radioactive substance free.
The amount of free isotope is then measured to see how much of the original substance was in the blood. This isotopic measuring method was developed in 1959 by two Americans, biophysicist Rosalyn Yalow (1921-) and physician Solomon A. Berson (1918-1972).
History
Yalow and Berson developed the first radioisotopic technique to study blood volume and iodine metabolism. They later adapted the method to study how the body uses hormones, particularly insulin, which regulates sugar levels in the blood. The researchers proved that Type II (adult onset) diabetes is caused by the inefficient use of insulin. Previously, it was thought that diabetes was caused only by a lack of insulin.
In 1959 Yalow and Berson perfected their measurement technique and named it radioimmunoassay (RIA). RIA is extremely sensitive. It can measure one trillionth of a gram of material per milliliter of blood. Because of the small sample required for measurement, RIA quickly became a standard laboratory tool.
How RIA Works
As an example of how this technique works, let's apply it to insulin. To measure insulin, the first step is to mix known amounts of radioisotope-tagged insulin and antibodies. These combine chemically. Next, a small amount of the patient's blood is added. The insulin contained in the blood displaces some of the tagged insulin. The free-tagged insulin is then measured with isotope detectors and the patient's insulin level is calculated.
A procedure that measures minute amounts of a substance, such as a hormone or drug, by quantitating the binding, or the inhibition of binding, of a radiolabeled substance to an antibody.
Radioimmunoassay (RIA) is a sensitive method for measuring very small amounts of a substance in the blood. Radioactive versions of a substance, or isotopes of the substance, are mixed with antibodies and inserted in a sample of the patient's blood. The same non-radioactive substance in the blood takes the place of the isotope in the antibodies, thus leaving the radioactive substance free.
The amount of free isotope is then measured to see how much of the original substance was in the blood. This isotopic measuring method was developed in 1959 by two Americans, biophysicist Rosalyn Yalow (1921-) and physician Solomon A. Berson (1918-1972).
History
Yalow and Berson developed the first radioisotopic technique to study blood volume and iodine metabolism. They later adapted the method to study how the body uses hormones, particularly insulin, which regulates sugar levels in the blood. The researchers proved that Type II (adult onset) diabetes is caused by the inefficient use of insulin. Previously, it was thought that diabetes was caused only by a lack of insulin.
In 1959 Yalow and Berson perfected their measurement technique and named it radioimmunoassay (RIA). RIA is extremely sensitive. It can measure one trillionth of a gram of material per milliliter of blood. Because of the small sample required for measurement, RIA quickly became a standard laboratory tool.
How RIA Works
As an example of how this technique works, let's apply it to insulin. To measure insulin, the first step is to mix known amounts of radioisotope-tagged insulin and antibodies. These combine chemically. Next, a small amount of the patient's blood is added. The insulin contained in the blood displaces some of the tagged insulin. The free-tagged insulin is then measured with isotope detectors and the patient's insulin level is calculated.
Uses for RIA :-
RIA has many uses, including narcotics (drug) detection, blood bank screening for the hepatitis (a highly contagious condition) virus, early cancer detection, measurement of growth hormone levels, tracking of the leukemia virus, diagnosis and treatment of peptic ulcers, and research with brain chemicals called neurotransmitters.
Radioimmunoassay Radioimmunoassay is an extremely sensitive method that can be used for the detection and quantitation of any substance that is antigenic and can be labelled with a radioactive isotope. Basically, the method depends upon the competition between labelled (known) and unlabelled (unknown)antigen for the same antibody. A known amount of labelled antigen, a known amount of specific antibody, and an unknown amount of unlabelled antigen are allowed to react together.The more of the antigen there is in the test sample, the less chance the labelled antigen has of combining with the limited number of antibody molecules that are available Thus by measuring the quantity of labelled antigen combined with antibody (with isotope counting equipment), a measure of the antigen in the unknown test sample can be obtained. The more labelled antigen combined with antibody, the lower the antigen level in the test sample.
The quantity of isotope-labelled antigen complexing with the antibody varies inversely with the quantity of unlabelled antigen in the test sample. In order to measure the amount of the labelled antigen attached to antibody, it is necessary to separate the antigen-antibody complexes from the mixture. A variety of methods have been developed to separate antibody-bound and unbound labelled antigen. However, the most convenient is the solid phase radioimmunoassay wherein the antibody is linked to an insoluble support, for example, agarose beads. The insoluble complex is then mixed with labelled and unlabelled test antigen. Antibody-bound, labelled antigen can then be separated from free antigen by centrifugation or filtration. By measuring the radioactivity, the percentage of labelled antigen bound to the antibody can be calculated. The concentration of an unknown (unlabelled) antigen can be determined by reference to a standard curve constructed from data obtained by allowing varying amounts of an labelled antigen to complete.
RIA has many uses, including narcotics (drug) detection, blood bank screening for the hepatitis (a highly contagious condition) virus, early cancer detection, measurement of growth hormone levels, tracking of the leukemia virus, diagnosis and treatment of peptic ulcers, and research with brain chemicals called neurotransmitters.
Radioimmunoassay Radioimmunoassay is an extremely sensitive method that can be used for the detection and quantitation of any substance that is antigenic and can be labelled with a radioactive isotope. Basically, the method depends upon the competition between labelled (known) and unlabelled (unknown)antigen for the same antibody. A known amount of labelled antigen, a known amount of specific antibody, and an unknown amount of unlabelled antigen are allowed to react together.The more of the antigen there is in the test sample, the less chance the labelled antigen has of combining with the limited number of antibody molecules that are available Thus by measuring the quantity of labelled antigen combined with antibody (with isotope counting equipment), a measure of the antigen in the unknown test sample can be obtained. The more labelled antigen combined with antibody, the lower the antigen level in the test sample.
The quantity of isotope-labelled antigen complexing with the antibody varies inversely with the quantity of unlabelled antigen in the test sample. In order to measure the amount of the labelled antigen attached to antibody, it is necessary to separate the antigen-antibody complexes from the mixture. A variety of methods have been developed to separate antibody-bound and unbound labelled antigen. However, the most convenient is the solid phase radioimmunoassay wherein the antibody is linked to an insoluble support, for example, agarose beads. The insoluble complex is then mixed with labelled and unlabelled test antigen. Antibody-bound, labelled antigen can then be separated from free antigen by centrifugation or filtration. By measuring the radioactivity, the percentage of labelled antigen bound to the antibody can be calculated. The concentration of an unknown (unlabelled) antigen can be determined by reference to a standard curve constructed from data obtained by allowing varying amounts of an labelled antigen to complete.
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