An alternative to allergy skin testing is blood testing, in which a small sample of a patient’s blood is tested for the presence of IgE antibodies. In the past, the testing assay was based upon a radiolabeled technology called the radioimmunosorbent test (RAST). More recently, laboratories have devised a new technique referred to as the ImmunoCAP test, which does not rely upon radioiso-topes.
The new test is considered quite accurate, but, compared with prick/puncture skin testing, it may miss up to 20% of IgE antibodies to selected allergens. Allergy blood tests can be performed even in the pres-ence of skin disease, and the test results are not affected by drugs such as antihistamines. The most significant criticism of this type of testing is the higher cost and necessity of waiting several days to weeks for the results.
Radioimmunosor-bent test (RAST)
A type of blood allergy test in which IgE antibodies to specific allergens are measured.