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ImmunoCAP Specific IgE Blood Test

ImmunoCAP Specific IgE Blood Test

Test Summary

ImmunoCAP® Specific IgE Blood Test

  

Clinical Use

  • Diagnose IgE-mediated allergic disorders

Clinical Background

Patients with IgE-mediated allergies may present with one or more of a broad range of non-specific symptoms including bronchospasm, 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 comorbid 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 test6:

  • The patient has a widespread skin disease

  • The patient has a high risk of anaphylaxis from skin testing

  • The patient is receiving medications (eg, beta-blockers; angiotensin-converting enzyme inhibitors; and some antihistamines and tricyclic antidepressants) that interfere with skin testing

  • The patient is uncooperative

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 Suitable for Testing

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.

Method

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. 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.

Interpretive Information

Clinically-used, published decision points for interpretation of in vitro IgE test results have been based on this ImmunoCAP method12,13; however, ImmunoCAP test results are not interchangeable with other in vitro IgE test results.14,15 Thus, published decision points apply only to the ImmunoCAP Specific IgE method.

References

  1. Holgate ST, Lack G. Improving the management of atopic disease. Arch Dis Child. 2005;90:826-831.

  2. National Asthma Education and Prevention Program. Expert Panel Report 3 (EPR-3): guidelines for the diagnosis and management of asthma–Summary Report 2007. J Allergy Clin Immunol. 2007;120(Suppl 5):S94-S138.

  3. Novembre E, Galli E, Landi F, et al. Coseasonal sublingual immunotherapy reduces the development of asthma in children with allergic rhinoconjunctivitis. J Allergy Clin Immunol. 2004;114:851-857.

  4. Möller C, Dreborg S, Ferdousi HA, et al. Pollen immunotherapy reduces the development of asthma in children with seasonal rhinoconjunctivitis (the PAT-study). J Allergy Clin Immunol. 2002;109:251-256.

  5. Warner JO, Early Treatment of the Atopic Child (ETAC) Study Group. A double-blind, randomized, placebo-controlled trial of cetirizine in preventing the onset of asthma in children with atopic dermatitis: 18 months' treatment and 18 months’ posttreatment follow-up. J Allergy Clin Immunol. 2001;108:929-937.

  6. Bernstein IL, Li JT, Bernstein DI, et al. Allergy diagnostic testing: an updated practice parameter. Ann Allergy Asthma Immunol. 2008;100(Suppl 3):S1-S148.

  7. Joint Task Force on Practice Parameters. Food allergy: a practice parameter. Ann Allergy Asthma Immunol. 2006;96:S1-S68.

  8. Alonso R, Botey J, Pena JM, et al. Specific IgE determination using the CAP system: comparative evaluation with RAST. J Investig Allergol Clin Immunol. 1995;5:156-160.

  9. Leimgruber A, Mosimann B, Claeys M, et al. Clinical evaluation of a new in-vitro assay for specific IgE, the immuno CAP system. Clin Exp Allergy. 1991;21:127-131.

  10. Bousquet J, Chanez P, Chanal I, et al. Comparison between RAST and Pharmacia CAP system: a new automated specific IgE assay. J Allergy Clin Immunol. 1990;85:1039-1043.

  11. Williams PB, Barnes JH, Szeinbach SL, et al. Analytic precision and accuracy of commercial immunoassays for specific IgE: establishing a standard. J Allergy Clin Immunol. 2000;105:1221-1230.

  12. Sampson HA. Utility of food-specific IgE concentrations in predicting symptomatic food allergy. J Allergy Clin Immunol. 2001;107:891-896.

  13. Perry TT, Matsui EC, Conover-Walker MK, et al. The relationship of allergen-specific IgE levels and oral food challenge outcome. J Allergy Clin Immunol. 2004;114:144-149.

  14. Wang J, Godbold JH, Sampson HA. Correlation of serum allergy (IgE) tests performed by different assay systems. J Allergy Clin Immunol. 2008;121:1219-1224.

  15. Wood RA, Segall N, Ahlstedt S, et al. Accuracy of IgE antibody laboratory results. Ann Allergy Asthma Immunol. 2007;99:34-41.

Content reviewed 04/2013

 
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