If you suspect you or your child(ren) have one or more food allergies, an allergist may recommend IgE RAST test to confirm whether the suspect symptoms are true food allergies.
If your allergist determines your suspect symptoms are a sign of a true food allergy, your allergist will decide which foods you should be tested on. If you are unsure of the specific food you may have reacted to, your allergist may request an IgE RAST test for a broad range of foods.
What is an IgE RAST Test?
An IgE RAST test (short for radioallergosorbent test) is a blood test used to detect specific IgE antibodies to suspected or known allergens. IgE is the antibody associated with Type I allergic response.
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.
Source: RAST Test, Wikipedia
IgE RAST Test Results for Food Allergies
IgE RAST test results are usually returned in units of micrograms per milliliter (μg/mL), and some test results include a class rating scale, often from 0 to 6.
On rated tests, class 0 almost always indicates a low chance of a true food allergy, while the higher numbers normally mean a very strong chance of allergy and a strong likelihood of a severe reaction. An allergist can use these results to help determine your treatment or to see whether a person is showing signs of outgrowing a food allergy.
Submitting an IgE RAST test is relatively easy. A phlebotomist will draw the proper number of vials of blood-based on your allergist's recommendations, and send those vials to a qualified lab for testing. In a week or so, you will be notified by your allergist of the test results and any treatment that may be necessary.
Remember to always discuss all test results and treatment options with your allergist.