• Diagnose IgE-mediated allergic disorders

Patients with IgE-mediated allergies may present with one or more of a broad range of non-specific symptoms including bronchospasms, rhinitis, conjunctivitis, recurrent otitis media, urticaria, eczema, angioedema, pruritus, colic, nausea, abdominal pain, vomiting, diarrhea, or anaphylaxis. Such symptoms can also be consistent with viral and bacterial infections, medication side-effects, occupational irritants, hormones, emotional stress, etc. A definitive allergy diagnosis allows selection of appropriate therapies such as immunotherapy or allergen avoidance and circumvents use of unnecessary medication (eg, antibiotics) and unnecessary, costly, inconvenient, or potentially harmful (eg, food avoidance) avoidance measures.¹ A definitive allergy diagnosis can also enable improved management of co-morbid conditions such as asthma.² Additionally, early allergy diagnosis and treatment may delay or prevent development of asthma in children.^3-5 Thus, overall patient healthcare can be improved, leading to reduced morbidity and a higher quality of life.

Specific IgE allergen testing has been used clinically to rule in or rule out atopy in patients with allergy-like symptoms, identify the allergen causing the patient’s symptoms, and to assess current sensitivity/tolerance to the allergen in previously diagnosed patients. Skin testing has historically been the preferred method owing to higher sensitivity.⁶ However, the Joint Task Force on Practice Parameters, composed of the 3 national allergy and immunology societies, considers both skin testing and in vitro IgE tests to have sufficient sensitivity to help rule out IgE-mediated food allergies.⁷ Moreover, there are certain circumstances in which an in vitro test should be used instead of a skin test: 1) the patient has a history of a life-threatening reaction (eg, anaphylaxis or unstable asthma); 2) the patient has a medical condition that prevents accurate skin testing (eg, extensive atopic dermatitis or dermatographism); 3) the patient is pregnant; 4) the patient is receiving long-acting antihistamines, tricyclic antidepressants, or medications that would need to be discontinued prior to skin testing; and 5) blood sampling (ie, 1 skin prick) is preferable to multiple skin pricks as in children and uncooperative patients with mental or physical impairment.^6,7

The ImmunoCAP Specific IgE is an in vitro IgE test, as is the older radioallergosorbent test (RAST). Studies comparing sensitivity of the 2 tests generally show superior sensitivity for the ImmunoCAP method.^8-10 In addition, ImmunoCAP, but not RAST, was shown to perform nearly as well as a theoretical ideal assay defined by multiple analytical features.¹¹ ImmunoCAP Specific IgE test results are rapidly available and do not require the patient to return to the physician's office for reading as do skin tests.

Individuals who present with a clinical history and physical symptoms consistent with IgE-mediated allergy are candidates for specific IgE testing. They may include:

• Infants with eczema

• Young children with asthma

• Older children and adults with rhinitis

• Those with a family history of allergy

The test can be used for patients 3 months of age and older, regardless of skin condition. There is no need to stop current medications prior to drawing a blood sample.

This fluorescent enzyme immunoassay (FEIA) measures allergen-specific immunoglobulin E (IgE) in human serum. It can measure IgE antibodies specific for animal, plant, and other allergens such as silk, latex, etc.

Specific IgE tests for over 200 allergens are available; each of these can be ordered individually (Table). Also available are panels designed to detect the most prevalent allergens while minimizing cost. Since the most prevalent allergens causing respiratory symptoms vary geographically, Quest Diagnostics provides region-specific panels for inhalant allergens. Additional information can be found in the Quest Diagnostics Directory of Services.

Clinically-used, published decision points for interpretation of in vitro IgE test results have been based on this ImmunoCAP method^12,13; however, ImmunoCAP test results are not interchangeable with other in vitro IgE test results.^14,15 Thus, published decision points only apply to the ImmunoCAP Specific IgE method.