ImmunoCAP testing is preferred to RAST tests. ImmunoCAP is a blood test that can detect specific allergens in the blood. The sensitivity (accuracy) of these tests is about 70%. Therefore, skin test are superior and are presently the preferred tests/gold standard for diagnosis of IgE-mediated allergy. The ImmunoCAP test may be preferable in the following situations:
Testing in patients with severe dermatographism or widespread eczema.
Testing in patients who are currently taking long-acting antihistamines, tricyclic antidepressants, or medications that may put the patient at risk if they are discontinued.
For evaluation of cross-reactivity between insect venom
When clinical history suggest a high risk of anaphylaxis from skin testing.
To follow patient with food allergies to help determine when food challenges may be performed in an attempt to re-add allergic foods back to the diet.