Food allergy panel testing often leads to misdiagnosis

To determine the utility of food allergy panel testing among patients referred to a pediatric food allergy center, investigators conducted a retrospective chart review of such patients for whom a primary care provider had obtained a standard panel of immunoglobulin E (IgE) tests.

Of a total of almost 800 patient encounters, a standard panel of food-specific IgE tests was performed in 284 (35%). Of 274 in whom the tests were performed (10 charts were excluded for not meeting study guidelines), only 90 (32.8%) had a history warranting evaluation for food allergy, according to National Institute of Allergy and Infectious Diseases (NIAID) guidelines: a history of symptoms consistent with allergy occurring after ingesting food or moderate-to-severe atopic dermatitis (AD). Most often the reason for ordering the test in those without a history of IgE-mediated food allergy was allergic rhinitis, followed by mild AD and idiopathic urticaria.

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Although 126 individuals were avoiding a food based on recommendations from the referring provider, under the guidance of the center 112 (88.9%) were able to reintroduce at least 1 food into their diets, with an average of 2 foods reintroduced per patient. Further, of the 274 individuals tested, a previously unknown allergen was identified in only 42, most often milk, egg, or peanut.

Investigators determined that the positive predictive value (PPV) of food allergy panel testing in the study population was 2.2%, and that the estimated cost of evaluating these patients, including serum and skin-prick testing and observed food challenges, was $79,412 (Bird JA, et al. J Pediatr. 2015;166[1]:97-100).

Commentary: The PPV, the likelihood that a positive test result is a true positive, is affected by the prevalence of the disease in the population tested. This value was low in the study population because the tests were done on many children who were unlikely to have true IgE mediated food allergy (eg, those with allergic rhinitis, mild AD, or urticaria). Rather, a positive test is more likely to represent true food allergy in higher-risk children as defined by NIAID guidelines. The message here is that availability of serum IgE food allergy panels is not an indication for ordering them. In an accompanying editorial, Fleisher and Burks make clear recommendations on how to diagnose food allergy based on a careful history and physical examination along with limited testing. It may be worth reading this helpful editorial (J Pediatr. 2015;166[1]:8-10) before you next order a serum IgE panel for foods and certainly before you prescribe a food elimination diet. -Michael G Burke, MD

Ms Freedman is a freelance medical editor and writer in New Jersey. Dr Burke, section editor for Journal Club, is chairman of the Department of Pediatrics at Saint Agnes Hospital, Baltimore, Maryland. The editors have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.