Radio immunoassayRadioimmunoassay

Angel CruzElyssa RondaErick AlemanErik Hetman

History•Radioimmunoassay (RIA) is a very sentive technique to measure amounts of antigen by the use of antibodies. •The RIA technique requires very specific and special equpitment, but to this day remains one of the cheapest methods of performing the test. •Lately it has been replaced by the ELISA method which uses Colorimetric signals instead of radioactive signals. But the RIA method still remains the most consistent and low priced.•The technique was developed by Rosalyn Yalow and Soloman Aaron Berson, in the 1950s. •In 1977 Yalow won the Nobel Prize in Medicine for the RIA for Insulin. •Yalow and Berson did NOT patent their discovery because they felt it would be best for medicine if it was available to everyone.

•One example of an RIA test is the Rast test. •The Rast test is a blood test that is used to determine what substances a person is allergic to.•It is a least common way of detecting allergies, compared to a skin allergy test. •The suspected allergen (substance that can cause allergies) is bound to an insoluble material and then the patient’s serum is added. If the patient’s serum has antibodies for the allergen then those antibodies will bind to the allergen. •Then Radio labeled anti-human IgE (immunoglobin E, a type of antibody) is added to the binded antibodies that are present. Afterwards, the unbound antihuman IgE antibodies are washed away. Then the amount of radioactivity that is left is the same amount as the serum’s IgE for the specific allergen.

The RAST Test

How it’s made

•Most RIA methods have 125 iodine (125I) as the radiolabel. •This isotope emits gamma rays. It has high specific activity so small doses can be used and has a short half-life of 60 days. •These properties create minimal disposal problems with leftover reagents. Gamma rays emitted by the protected complexes are usually measured after the removal of unbound (free) radiolabel.• The background radiation is very low making The RIA method the most sensitive of all immunoassay methods.

Strengths VS. Weaknesses

Strengths• Radioimmunoassay is a highly sensitive test.• The test can even detect very little pictograms of the antigen.• It is a helpful tool in clinical laboratories.

Weaknesses•The antigen used is radioactive• It takes time and money in order to handle the radioactive antigen carefully.• Special equipment is needed in order to count the gamma radiation that is emitted.

Case 1

In 1988 the New York state court was in a split decision when they were reviewing a case where a woman wanted custody of her children but needed to be proven drug substance free. The RIA test was able to detect cocaine through her hair samples. The court wanted more physical evidence but forensic science professor Dr. Fredrick Paul Smith, proved that the test results for the hair samples was still valid in court even if it was scientific evidence not hard physical evidence.

Case 2

One year a clinical study was done in western Scotland to figure out if farmer’s had lung syndrome that was said to be created over time. Three serology tests were done Radioimmunoassay being one of them. When they applied the radioimmunoassay test to the group of farmers researchers successfully detected high antibody levels in all with clinical evidence of farmer's lung syndrome; farmers who had no symptoms of the disease also had measurable antibody. This study shows the advantages of a quantitative test for antibodies.

Who developed the technique of RIA and when?

Review questions

Rosalyn Yalow and Solomon Aaron

Berson developed this technique in the

1960 for insulin.

In order to perform a

radioimmunoassay, what must be

done to a known antigen?

The antigen must be made radioactive.

What does the RIA test measure

and how?

The RIA test measures the

concentration of antigens by use of

antibodies.

What are some advantages and disadvantages of

the RIA test?

AdvantagesThe test provides sensitive and specific data.Least expensive.

DisadvantagesNeeds special precaution and license because of radioactive material.

What is a type of test that comes

from the RIA method?

The Rast test

What is the radiolabel for

RIA?

Iodine

http://medind.nic.in/ibr/t00/i2/ibrt00i2p97.pdf

http://www.drugtestingnetwork.com/court-cases.htm

http://www.nytimes.com/1988/10/28/nyregion/court-allows-testing-of-hair-for-cocaine.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Radioimmunoassay.html

http://www.enotes.com/immunoassay-tests-reference/immunoassay-tests-172079

http://www.ncbi.nlm.nih.gov/pubmed/813924

Sources