Overdiagnosis of Food Allergy in Children

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.




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