Download radioimmunoassay - OldForensics 2012-2013

Radio
immuno
assay
Radioimmunoassay
Angel Cruz
Elyssa Ronda
Erick Aleman
Erik 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•Lately it has been replaced by the ELISA method which uses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.
The RAST Test
•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.
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.
Review questions
Who developed the
technique of RIA
and when?
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?
Advantages
The test provides sensitive and
specific data.
Least expensive.
Disadvantages
Needs 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
Sources
http://www.drugtestingnetwork.com/court-cases.htm
http://www.nytimes.com/1988/10/28/nyregion/court-allows-testingof-hair-for-cocaine.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Radioim
munoassay.html
http://www.enotes.com/immunoassay-testsreference/immunoassay-tests-172079
http://www.ncbi.nlm.nih.gov/pubmed/813924