COMMENTARY

Overdiagnosis of Food Allergy in Children

William T. Basco, Jr., MD

Disclosures

May 31, 2011

Oral Food Challenges in Children With a Diagnosis of Food Allergy

Fleischer DM, Bock SA, Spears GC, et al
J Pediatr. 2011;158:578-583.e1. Epub 2010 Oct 28.

Study Summary

Food allergies have increased substantially over the past decade. Practitioners are more commonly using commercially available immunoglobulin E (IgE) testing in office settings, leading many parents to institute dietary restrictions for their children. Fleischer and coworkers were concerned that many of these dietary restrictions are unnecessarily. They point out that the gold-standard test for food allergy is still the double-blind, placebo-controlled food challenge.

To estimate the necessity of food-restriction diets prescribed by nonimmunologists, the investigators conducted a retrospective chart review of patients seen at a single referral hospital. The children were seen from 2007 through 2008 in the pediatric food allergy and eczema program at the institution. The investigators identified children who had at least 1 oral food challenge during the study period. When the children were referred to the immunology center for testing, the immunologists reviewed all history, examination, and laboratory data from previous evaluations. In children with atopic dermatitis, the referral clinic initiated a protocol to get the atopic dermatitis under control before initiating skin testing and subsequent oral food challenges. After maximizing control of atopic dermatitis, the children underwent skin-prick testing against the foods to which they were reported to be allergic. In addition, food-specific IgE levels were obtained. In general, the referral center did not complete an oral food challenge if the patient had a history of a life-threatening reaction (eg, anaphylaxis) or if the child had experienced a reaction of any type in the past 6-12 months. For the oral food challenges, children were given escalating doses of the problematic food at 15- to 30-minute intervals. The investigators defined a negative food challenge as no reaction for at least 2 hours after completing the challenge. They considered any oral food challenge positive if the child developed any type of allergic reaction that would indicate IgE-mediated symptoms such as urticaria, angioedema, tightness in the throat, wheezing, vomiting, or diarrhea. More than 95% of the children had active atopic dermatitis at the initial evaluation and required treatment for their atopic dermatitis before initiating food challenges. The study's 125 children completed 364 total oral food challenges, of which 325 (89%) were negative. No reaction to oral food challenge began after 2 hours of observation.

When considering the foods that children were avoiding on the basis of IgE testing or skin-prick testing, it is notable that 93% of oral challenges to these foods were negative. In contrast, 84% of the oral food challenges were negative for foods that were being avoided because the children had a history of a previous reaction. Among foods that were being avoided because of IgE or skin-prick testing (meat, milk, oats, shellfish, and vegetables) none were associated with a positive oral food challenge. With respect to foods that were being avoided on the basis of a previous reaction, more of these were associated with a positive food challenge. The notable exceptions in that group were fruit and shellfish, which were not associated with positive oral food challenges. The investigators make a point that in both groups, the foods associated with positive food challenges tended to be those classically considered common food allergens, such as egg, peanut, soy, and wheat. Of interest, the only positive oral food challenges to fruits were in 2 children who had reactions to banana. Most children who had positive IgE, skin-prick testing, or reported previous reaction to milk were able to tolerate oral food challenge with milk. Fleischer and coworkers concluded that many children are unnecessarily placed on restrictive food diets on the basis of serum food-specific IgE testing or skin-prick testing. They suggest that the oral food challenge is an appropriate approach in certain children rather than prescribing restrictive diets.

Viewpoint

This is a very interesting study, and my only comments are to reiterate 2 very important points that Fleischer and colleagues make in their discussion. First, the in-office use of IgE testing and skin-prick testing may very well be something that should be confined to the realm of experts. Although it may be possible for generalists or other specialists to do in-office testing, these data suggest that the results of these studies are nonspecific with respect to identifying children who would have real allergic reactions. Although it is difficult to know whether the experience of these 125 patients is representative of a larger group, it is concerning to think how many children may be on food-elimination diets as a result of such nonspecific testing. Therefore, it would seem to be a good clinical rule of thumb that, should a nonspecialist conduct office testing and prescribe elimination diets, such a prescription should also be accompanied by a referral to an appropriate specialist who can adequately interpret all of the clinical and laboratory data and perhaps conduct a food challenge to determine whether such elimination diets are necessary.

Abstract

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