Method
The RAST test is a radioimmunoassay test to detect specific IgE antibodies to suspected or known allergens for the purpose of guiding a diagnosis about allergy. IgE is the antibody associated with Type I allergic response: for example, if a person exhibits a high level of IgE directed against pollen, the test may indicate the person is allergic to pollen (or pollen-like) proteins. A person who has outgrown an allergy may still have a positive IgE years after exposure.
The suspected allergen is bound to an insoluble material and the patient's serum is added. If the serum contains antibodies to the allergen, those antibodies will bind to the allergen. Radiolabeled anti-human IgE antibody is added where it binds to those IgE antibodies already bound to the insoluble material. The unbound anti-human IgE antibodies are washed away. The amount of radioactivity is proportional to the serum IgE for the allergen.
RAST are often used to test for allergies when:
• a physician advises against the discontinuation of medications that can interfere with test results or cause medical complications;
• a patient suffers from severe skin conditions such as widespread eczema or psoriasis; or
• a patient has such a high sensitivity level to suspected allergens that any administration of those allergens might result in potentially serious side effects.
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