-- Question: Are different types of RASTs like IgG RASTs useful?
Answer: There are different types of serum test to measure allergy antibody. These are known as radioallergosorbant test or RAST test. The most reliable RAST test is the type of RAST called the immunoCAP RAST.
This can measure specific food allergens in an IgE fashion or an IgG fashion -- those are the two types of antibodies. The most reliable and the only one that has scientific proof and data associated with clinical reactions in patients are the IgE RAST. IgG RAST have not been studied in relationship to food allergy and are not known to have any correlation with a patient's response to that food.
So in other words, if your doctor is using a RAST test to diagnose your food allergy, it should be specific to IgE antibodies to that food and not IgG.