FROM THE AMERICAN ACADEMY OF PEDIATRICS Guidance for the Clinician in Rendering Pediatric Care CLINICAL REPORT Allergy Testing in Childhood: Using Allergen-Specific IgE Tests Scott H. Sicherer, MD, Robert A. Wood, MD, and the SECTION ON ALLERGY AND IMMUNOLOGY abstract KEY WORDS A variety of triggers can induce common pediatric allergic diseases allergy, allergy testing, immunoglobulin, IgE, immunotherapy, which include asthma, allergic rhinitis, atopic dermatitis, food allergy, pediatrics and anaphylaxis. Allergy testing serves to confirm an allergic trigger ABBREVIATIONS fi IgE—immunoglobulin E suspected on the basis of history. Tests for allergen-speci c immuno- sIgE—allergen-specific IgE globulin E (IgE) are performed by in vitro assays or skin tests. The tests SPT—skin prick test are excellent for identifying a sensitized state in which allergen-specific — IgG immunoglobulin G IgE is present, and may identify triggers to be eliminated and help This document is copyrighted and is property of the American guide immunotherapy treatment. However, a positive test result does Academy of Pediatrics and its Board of Directors. All authors have filed conflict of interest statements with the American not always equate with clinical allergy. Newer enzymatic assays based Academy of Pediatrics. Any conflicts have been resolved through on anti-IgE antibodies have supplanted the radioallergosorbent test a process approved by the Board of Directors. The American (RAST). This clinical report focuses on allergen-specific IgE testing, em- Academy of Pediatrics has neither solicited nor accepted any commercial involvement in the development of the content of phasizing that the medical history and knowledge of disease character- this publication. istics are crucial for rational test selection and interpretation. Pediatrics The guidance in this report does not indicate an exclusive 2012;129:193–197 course of treatment or serve as a standard of medical care. Variations, taking into account individual circumstances, may be INTRODUCTION appropriate. Allergic diseases (allergic rhinitis [hay fever], asthma, atopic der- All clinical reports from the American Academy of Pediatrics automatically expire 5 years after publication unless reaffirmed, matitis, and allergic or anaphylactic reactions to foods, drugs, insect revised, or retired at or before that time. venom, or other allergens) often warrant identification of specific allergic triggers for treatment. Most allergic responses are mediated by immunoglobulin E (IgE) antibodies specific for the trigger allergen, which can be detected with in vitro tests or skin testing. This clinical report focuses on using in vitro allergen-specific IgE (sIgE) testing, which is widely available to pediatricians. A full description of the use of tests for diagnosis and management of allergic disease is beyond the scope of this report, but is described in recent guidelines and practice parameters.1–9 www.pediatrics.org/cgi/doi/10.1542/peds.2011-2382 TESTS AVAILABLE FOR DETECTING sIgE doi:10.1542/peds.2011-2382 A number of enzymatic assays that are based on anti-IgE antibodies PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). have supplanted the radioallergosorbent test.10 Commercial labora- Copyright © 2012 by the American Academy of Pediatrics tories that are federally licensed under the Clinical Laboratory Im- provement Act of 1988 often use automated systems capable of detecting and quantifying sIgE. Laboratory reports may indicate a number of readouts (eg, classes, counts, or units), but quantifica- tion of results in units reflecting concentrations of sIgE is becoming more common (eg, kUA/L). Although the 3 commercial detection sys- tems approved by the Food and Drug Administration have excellent performance characteristics (analytical sensitivity, 0.1 kUA/L), the PEDIATRICS Volume 129, Number 1, January 2012 193 Downloaded from www.aappublications.org/news by guest on September 26, 2021 individual systems appear to detect specific trigger when there is suspicion which increases diagnostic value by different populations of IgE antibody of one, or in less common circum- applying previous probability.4 or do not measure IgE antibodies with stances, screening for atopy. A positive A physician interested in screening for comparable efficiencies. Thus, a result serum sIgE or skin test denotes a sen- atopy (eg, distinguishing recurrent viral foranallergenin1ofthe3testsystems sitized state. However, detection of sen- infections from allergic rhinitis) might may not be equivalent to the same al- sitization to an allergen is not equivalent select a small panel of common trig- lergen tested in a different system. to a clinical diagnosis. In fact, many gers. Another means to screen for at- The skin prick test (SPT), typically used children with positive tests have no opy is to use a multiallergen test that by allergy specialists, is another clinical illness when exposed to the contains several common allergens in means of detecting sIgE antibodies.11 A allergen.2,3,7,9,11,13 This limitation high- one test (eg, one test that includes number of devices are available for lights the need for the clinician to several perennial allergens, such as introducing allergen into the surface use a detailed medical history and dust mite, dog dander, and mold). of the skin with minimal discomfort; have knowledge of the features of the Availability and composition of these a resulting wheal-and-flare response specific illness when selecting and in- tests varies by manufacturer. A posi- canbemeasuredin10to20minutes. terpreting tests. For example, there is tive result will not identify IgE to a Saline and histamine controls are no need to test for an allergen that is specific antigen but can, at less cost placed for comparison. Intradermal clearly tolerated (eg, egg in a child than performing many individual tests, skin testing is performed in special who eats egg without symptoms) or identify a child whose symptoms may circumstances when increased sensi- when exposure is not relevant (eg, relate to exposure to a specific allergen tivity is required (eg, after negative testing a pollen to which the child is and warrant further specifictestingor SPT for vaccines, venom, penicillin, not geographically exposed). Knowl- referral. The multiallergen test had and some inhalant allergens, such as edge of local aerobiology is, therefore, excellent predictive value for identifying Alternaria organisms and perhaps essential. Testing large panels of aller- atopic children compared with SPTs 14,15 other outdoor molds). gens without consideration of the his- and an allergist’s diagnosis. Both serum sIgE tests and SPT are tory, geographic relevance, and disease sensitive and have similar diagnostic characteristics may result in many ISSUES SPECIFIC TO RESPIRATORY properties.11,12 Advantages of the SPT clinically irrelevant positive results, ALLERGY1,6,11 include immediate results visible to the which, if overinterpreted, may lead to The disorders that respiratory allergy patient/family and low cost compared costly and socially, emotionally, and/or comprises are allergic asthma and with serum sIgE tests. Disadvantages nutritionally detrimental actions of un- seasonal or perennial allergic rhinitis. include the need to withhold medi- necessary allergen avoidance. Similarly, National asthma guidelines1 suggest cations with antihistamine properties caution is advised when testing is neg- that patients with persistent asthma and having rash-free skin available for ative despite a convincing history. Test- be evaluated for the role of allergens testing. Advantages of the serologic ingforsIgEwouldalsogenerallynotbe as contributing factors, with an em- tests include availability and lack of useful when the disorder has no path- phasis on testing for perennial indoor interference from antihistamines or ophysiological basis for a relationship allergens (eg, dust mite, animal dan- extensive dermatitis. Disadvantages to sIgE (eg, behavioral disorders; aller- der, cockroach, mold) that might other- include the need to obtain blood sam- gic disorders not related to sIgE, such wise not be identified as contributing ples, delayed results, and cost. Some as allergic contact dermatitis). to disease and also suggest testing discrepancies exist, however; one test Few studies have correlated clinical seasonal or perennial allergens for or the other may be more sensitive to outcomes to test results.2,3,4,11 Studies selected patients with any level of detect specific allergens, probably be- have generally supported the notion asthma severity as a basis for edu- cause different proteins or IgE binding that increasingly strong tests correlate cation about the role of allergens for sites are represented.2,3,7,9,11,13 with increasing likelihood of clinical re- avoidance and for immunotherapy. activity.2,3,11 Patients should not be told The clinician may be interested in TEST SELECTION AND they are allergic based solely on either identifying specific indoor (eg, dust INTERPRETATION a skin test or the identification of sIgE. mite, animal dander, molds, mice, and Tests might be selected to identify The test characteristics underscore the cockroach) or outdoor (eg, pollens, triggers from a number of potential need to select and interpret tests with molds) triggers. Rational selection common allergens, for confirming a consideration of the medical history, and interpretation of specifictests 194 FROM THE AMERICAN ACADEMY OF PEDIATRICS Downloaded from www.aappublications.org/news by guest on