Overdiagnosis of Food Allergy in Children

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Study Summary www.medscape.com

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 <http://www.medscape.com/medline/abstract/21030035>

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Ortiz, MS, RD

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