A well-designed oral food challenge (OFC) is the most reliable diagnostic test for infants whose clinical history and physical examination suggest a specific food allergy (strength of recommendation [SOR]: C, consensus guidelines)

Benveniste, Sara

Neher, Jon O.

Safranek, Sarah

University of Missouri: MOspace

Evidence-based answers from the Family Physicians Inquiries Network408 THE JOURNAL OF FAMILY PRACTICE  |   JULY 2010  |   VOL 59, NO 7For infants whose clinical history and physical exam suggest a specifi c food allergy, a well-designed oral food challenge is the most reliable test.EVIDENCE-BASED ANSWERASara Benveniste, MD; Jon O. Neher, MDValley Family Medicine Residency, Renton, WashSarah Safranek, MLISUniversity of Washington Health Sciences Library, Seattle What’s the best approach to diagnosing food allergies in infants? a well-designed oral food chal- lenge (OFC) is the most reliable diagnostic test for infants whose clinical history and physical examination suggest a specifi c food allergy (strength of recommen-dation [SOR]: C, consensus guidelines). Serum-specifi c immunoglobulin E (IgE), atopy patch testing (APT), and skin prick testing (SPT) are all alternatives to OFC, but the likelihood ratios are not ro-bust and the tests vary widely in sensitiv-ity and specifi city to diff erent allergens. For diagnosing egg and milk allergies, larger wheal sizes with SPT are more pre-dictive of a positive OFC (SOR: C, ex-trapolated from cohort studies evaluating mixed populations of infants, children, and teenagers). Evidence summaryTh e American Academy of Allergy, Asthma and Immunology (AAAAI) states that a dou-ble-blind, placebo-controlled OFC is the best test for diagnosing infants clinically suspected of having food allergies (that is, who develop gastrointestinal symptoms after eating a spe-cifi c food). However, performing an OFC in an infant is often diffi  cult and potentially danger-ous, especially if a severe allergy is suspected; testing also may eliminate nutritious foods, such as milk and eggs, from the infant’s diet.1 For these reasons, physicians have sought simpler alternatives to the OFC. Comparisons of serum and skin testing with OFCs produce variable, weak resultsTwo large cohort studies compared OFCs with serum and skin testing in infants, children, and teenagers. Overall, serum and skin testing didn’t produce robust results and the results varied with the antigen (TABLE). In 1 study, researchers compared specifi c serum IgE levels with OFC results for 4 foods—milk, eggs, wheat, and soy—in 501 consecu-tive pediatric patients referred to an allergy ward based on clinical or parental suspicion of food allergy. Children ranged in age from 1 month to 16 years (median age 13 months); results for infants were not provided separate-ly. Eighty-eight percent of the children were atopic. Investigators measured serum IgE (using the Pharmacia CAP-system fl uores-cence enzyme immunoassay) before adminis-tering the OFCs. Of 992 OFCs performed, 445 (45%) were positive (defi ned as producing urticaria, angio-edema, wheezing, vomiting, diarrhea, abdomi-nal pain, shock, or exacerbation of eczema). Most OFCs (73%) were double-blind placebo-controlled, but investigators performed open OFCs in infants and in children with a history of immediate allergic reactions. Investigators ret-rospectively analyzed serum-specifi c IgE levels for the 4 food antigens and compared them with the results of the OFCs. Positive likelihood ratios (LR+) for IgE testing ranged from 1.3 to 2.0 for the 4 antigens; negative likelihood ratios (LR−) ranged from 0.31 to 0.59.2Th e second cohort study compared APT and SPT with OFCs for the same 4 food anti-gens (milk, eggs, wheat, soy) in 437 children. Th e study population comprised consecutive referrals to a pediatric immunology depart-409JFPONLINE.COM VOL 59, NO 7  |  JULY 2010  |  THE JOURNAL OF FAMILY PRACTICESerum and skin testing offer alternatives to an oral food challenge, but have weak likelihood ratios and wide variations in sensitivity and specifi city to different allergens.ment based on either parental suspicion of a food allergy or a positive IgE test. Th e chil-dren ranged in age from 3 months to 14 years (median age 13 months); results for infants weren’t provided separately. Ninety percent of the children were atopic. Investigators per-formed APTs and SPTs for the 4 food antigens on all children and OFCs only for foods that were clinically suspect (total OFCs=873). As in the previous study, investigators performed open OFCs (23%) in infants and children with a history of immediate reaction. A positive APT was defi ned by erythema with infi ltration or papules, and a positive SPT by a wheal ≥3 mm. For the SPT, the LR+ ranged from 1.9 to 2.8 for the 4 antigens, and the LR− ranged from 0.13 (for egg) to 0.84. For the APT, the LR+ ranged from 1.6 to 6.2 (for milk), whereas the LR− was of little value, ranging from 0.68 to 0.90.3For milk and eggs, the larger the wheal, the more sensitive the skin test Th e size of the wheal may increase the sensi-tivity of the SPT in some situations. A cohort study similar to the ones described previously compared SPT with OFCs in children with possible food allergies and found that a large SPT wheal was highly correlated with OFC-confi rmed allergy to milk and eggs.4 Investigators recruited 385 children—3 months to 14 years of age (median age 22 months), results for infants not provided separately—from consecutive referrals to a pediatric immunology department. Most children (87%) were atopic. Investigators per-formed SPTs, followed by OFCs for milk, egg, wheat, and soy allergens. Overall, 312 (43%) of the OFCs were positive. Wheals measuring ≥13 mm for eggs and ≥12.5 mm for milk corre-lated well with OFC results (95% positive pre-Test* Sensitivity (%) Specifi city (%) LR+ LR-Milk             IgE2 83 53 1.8 0.32             SPT3 85 70 2.8 0.21             APT3 31 95 6.2 0.73Egg             IgE2 97 51 2.0 0.59             SPT3 93 54 2.0 0.13             APT3 41 87 3.2 0.68Wheat              IgE2 79 38 1.3 0.55              SPT3 75 64 2.1 0.39              APT3 27 89 2.5 0.82Soy               IgE2 69 50 1.4 0.31               SPT3 29 85 1.9 0.84               APT3 23 86 1.6 0.90APT, atopy patch test; IgE, serum immunoglobulin E; LR+, positive likelihood ratio; LR−, negative likelihood ratio; SPT, skin prick test.*Positive tests were defi ned as follows:    IgE=serum level >0.35 kU/L (detection limit of assay).   SPT=wheal ≥3 mm.    APT=erythema with skin surface change.TABLEHow allergy tests in infants and children compare with an oral food challenge410 THE JOURNAL OF FAMILY PRACTICE  |   JULY 2010  |   VOL 59, NO 7Referencesdictive value). Wheal sizes for wheat and soy were poorly predictive, however.4No validation yet for new techniques to improve accuracy and safety New techniques to improve the accuracy and safety of allergy testing have yet to be validat-ed clinically. One cohort study of 58 children that used fresh fruit or vegetable preparations for SPT instead of commonly used commer-cial extracts found added sensitivity.5 Another cohort study of 142 children allowed suspect foods to contact only the labial mucosa in or-der to reduce the risk of systemic reactions (1 case of anaphylaxis occurred nevertheless).6Recommendations Th e AAAAI guidelines state that history and physical examination help determine that food is causing symptoms and that an OFC is diag-nostic of food allergy (but risks and benefi ts must be considered, including the possibility of severe adverse reaction).1 Th e guidelines note that other available tests, including food-spe-cifi c IgE and skin tests, are not specifi c enough for screening but may be used when a particu-lar food allergy is clinically suspected.             JFP 1.   American College of Allergy, Asthma, and Immunology. Food allergy: a practice parameter. Ann Allergy Asthma Immunol. 2006;96(3 suppl 2):S1-S68.  2.   Celik-Bilgili S, Mehl A, Verstege A, et al. Th e predictive value of specifi c immunoglobulin E levels in serum for the outcome of oral food challenges. Clin Exp Allergy. 2005;35:268-273. 3.   Mehl A, Rolinck-Werninghaus C, Staden U, et al. Th e atopy patch test in the diagnostic workup of suspected food-relat-ed symptoms in children. J Allergy Clin Immunol. 2006;118:923-929.  4.   Verstege A, Mehl A, Rolinck-Werninghaus C, et al. Th e predictive value of the skin prick test weal size for the outcome of oral food challenges. Clin Exp Allergy. 2005;35:1220-1226.  5.   Cantani A, Micera M. Th e prick by prick test is safe and reliable in 58 children with atopic dermatitis and food allergy. Eur Rev Med Pharm Sci. 2006;10:115-120.  6.   Rance F, Dutau G. Labial food challenge in children with food al-lergy. Pediatr Allergy Immunol. 1997;8:41-44. What do I need         to know about gout?This CME supplement and supporting webcast discuss: •   The risk factors and comorbidities that contribute to and exacerbate acute gout fl ares•  Criteria for establishing a diagnosis of gout •   How to establish goals for achieving, sustaining, and monitoring clinically meaningful urate lowering •   Means for optimizing patient adherence to long-term urate-lowering treatmentThe supplement and audiocast were submitted by the Primary Care Education Consortium and supported by an educational grant from Takeda Pharmaceuticals North America, Inc.>> MICHAEL A. BECKER, MD>> GARY E. RUOFF, MDClick on Supplements/CME at jfponline.com. Or, visit www.jfponline.com/supplements.asp?id=8724FREE1.0 CME CREDITFor more information on gout, listen to a practical , engaging conversation between 2 family physicians—Stephen A. Brunton, MD, FAAFP, and Gary E. Ruoff , MD—Clinical conversations: What do I need to know about gout? http://www.jfponline.com/pages.asp?id=8725 FREE0.5 CME CREDIT

What's the best approach to diagnosing food allergies in infants?

Abstract

Similar works

Full text

Available Versions

University of Missouri: MOspace