Diagnosis of Food Allergy: Epicutaneous Skin Tests, In Vitro Tests, and Oral Food Challenge
Food allergy is becoming an increasingly common diagnosis. Because of this increase in prevalence, it is imperative that physicians evaluating patients with possible adverse reactions to foods understand the currently available assays and how they should best be used to accurately diagnose the disease. Simple tests such as skin prick testing (SPT) and serum food-specific IgE testing are the most commonly used diagnostic tests to evaluate for IgE-mediated food reactions. However, these tests, which measure sensitization and not clinical allergy, are not without pitfalls, and their utility must be appreciated to avoid over- and underdiagnosis. Although the physician-supervised oral food challenge remains the gold standard for food allergy diagnosis, a careful medical history paired with SPT and serum food-specific IgE testing often can provide a reliable diagnosis. In this review, we examine the usefulness and pitfalls of SPT and serum food-specific IgE levels, as well as examine atopy patch testing and other emerging tests, such as component-resolved diagnostics and the basophil activation test. Finally, we describe the use of the double-blind, placebo-controlled oral food challenge as the current gold standard for food allergy diagnosis.
KeywordsFood allergy Food-specific IgE Skin prick testing Component-resolved diagnostics Basophil activation test Atopy patch test Oral food challenge
Dr. Sicherer is supported in part by grants from the National Institutes of Health/National Institute of Allergy and Infectious Diseases.
Dr. Sicherer has served as a consultant for the Food Allergy Initiative and has received honoraria from Quest Diagnostics. Dr. Lieberman reported no potential conflicts of interest relevant to this article.
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- 4.•• Schneider Chafen JJ, Newberry SJ, Riedl MA, et al.: Diagnosing and managing common food allergies: a systematic review. JAMA 2010, 303:1848–1856. This was a large systematic review of studies on food allergy epidemiology and diagnosis. Google Scholar
- 19.• 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. These are the practice parameters developed by the American Academy of Allergy Asthma and Immunology and American College of Allergy, Asthma and Immunology Joint Task Force. This is an exceptional guide for practicing clinicians on appropriate testing. Google Scholar
- 29.• Wainstein BK, Studdert J, Ziegler M, et al.: Prediction of anaphylaxis during peanut food challenge: usefulness of the peanut skin prick test (SPT) and specific IgE level. Pediatr Allergy Immunol 2010, 21:603–611. This was the first large-scale study evaluating the relationship between IgE levels and severity of reactions. The investigators continued challenges with the goal of eliciting more serious reactions so as to be able to show what was thought to be true, which is that increasing IgE is correlated with more severe reactions. Google Scholar
- 32.• Cox L, Williams B, Sicherer SH, et al.: Pearls and pitfalls of allergy diagnostic testing: report from the American College of Allergy, Asthma, and Immunology/American Academy of Allergy, Asthma and Immunology Specific IgE Task Force. Ann Allergy Asthma Immunol 2008, 101:580–592. This publication provides a more in-depth look at IgE testing and what the clinician should take into account when using IgE testing to diagnose allergy. Google Scholar
- 39.• Nicolaou N, Poorafshar M, Murray C, et al.: Allergy or tolerance in children sensitized to peanut: prevalence and differentiation using component-resolved diagnostics. J Allergy Clin Immunol 2010,125:191–197. This well-designed study furthers the possible role of CRD in determining sensitization versus clinical allergy. This study showed the importance of IgE binding to Ara h 2 in differentiating allergy from sensitization. Google Scholar
- 43.• Wang J, Lin J, Bardina L, et al.: Correlation of IgE/IgG4 milk epitopes and affinity of milk-specific IgE antibodies with different phenotypes of clinical milk allergy. J Allergy Clin Immunol 2010, 125:695–702. This study further defined the role of epitope binding and tolerance. Google Scholar
- 48.• Nowak-Wegrzyn A, Assa’ad AH, Bahna SL, et al.: Work group report: oral food challenge testing. J Allergy Clin Immunol 2009, 123(Suppl):S365–S383. This is the most up-to-date guide on how and when to perform OFC testing. Google Scholar