Definition of RAST

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RAST: An allergy test done on a sample of blood. The aim with RAST, as with skin tests, is to check for allergic sensitivity to specific substances.

In the test, the sample of blood is mixed with substances known to trigger allergies. The test measures the level of allergy antibodies (specific IgE antibodies) in the blood which are present if there is a allergic reaction.

RAST stands for RadioAllergoSorbent Test. The term RAST test is sometimes used but is redundant since it refers twice to "test."