Food Allergy: Consensus Report Stresses Diagnostic Accuracy

Pam Harrison

July 24, 2017

A consensus report on critical issues in food allergy was released by the National Academies of Sciences, Engineering, and Medicine. A summary of that report was published online July 24 in Pediatrics.

Scott H. Sicherer, MD, professor of pediatrics, allergy, and immunology, Icahn School of Medicine at Mount Sinai in New York City, and colleagues participated in the development of the consensus report, which was targeted to many different stakeholders in food allergy, including industry, government, and patients. The authors felt it was important to bring forth relevant highlights for physicians managing pediatric patients with possible food allergies.

"What we tried to do in this article is focus on a few of the critical things that pediatricians might be interested in and be thinking about," Dr Sicherer told Medscape Medical News.

"And it's very important for physicians to take a judicious history in the context of knowledge about food allergy and then judiciously select tests that make sense to confirm suspected allergies, rather than test with panels without any thought about the history and epidemiology of food allergy," he added.

One of the most relevant highlights of the report is the issue of diagnosis, the authors write.

"A serious misconception about food allergy diagnostics relates to equating a 'positive test result' by a serum food-specific [immunoglobulin E] (sIgE) blood test or skin prick having an allergy to the tested food," they explain. "These tests detect IgE antibodies to the food but are not typically intrinsically diagnostic," they add.

The authors cite a study in which 111 oral food challenges were performed in 44 children who were avoiding a specific food because they had tested positive on either an sIgE blood test or a skin prick test.

Results showed that 93% of this small group could tolerate the food they had been avoiding because of the "positive" allergen test. "It is clear that these tests are misunderstood by physicians," the current report authors write. However, physicians also risk underdiagnosing or misdiagnosing a true food allergy. Without confirmatory testing, an allergen could incorrectly be identified as the culprit, leading to a serious reaction if the child is again exposed to the true allergen.

"Medical history is key in diagnosis, and food allergy should be considered when allergic symptoms occur proximate (within minutes to hours) to ingestion of a specific food, especially when symptoms occur on more than 1 occasion," the authors write. Physicians involved in pediatric care also need to remember that not all food allergies evolve from the production of IgE antibodies, and these will be missed on IgE antibody-based tests. Examples of non-IgE-mediated allergies include protein-induced enterocolitis, symptoms of which start 2 hours after ingesting the offending food allergen, and allergic colitis, characterized by mucous-containing bloody stools.

In contrast, "food allergy is not a typical trigger of chronic asthma or chronic rhinitis in childhood," the researchers note.

Definitive Test

The oral food challenge or feeding test is the definitive test to confirm an infant or child really does have a food allergy, Dr Sicherer said. "But in the vast majority of cases, a food allergy can be excluded or diagnosed with pretty good accuracy when you put together a careful history and [either sIgE or skin prick] testing," he said. A feeding test is really only needed when the patient's history or test results or both are ambiguous.

"Then you need to add the food back to the diet to see if it might trigger a serious reaction, but this has to be supervised by an allergist," Dr Sicherer said. Tests that are not recommended by the National Academies of Sciences, Engineering, and Medicine are many and varied in number, but include unproven and nonstandardized tests such as lymphocyte stimulation, facial thermography, gastric juice analysis, hair analysis, electrodermal testing, bioresonance, and iridology.

Newer thinking about allergy prevention includes the relatively recent endorsement of introducing allergenic foods in an infant's diet earlier than was previously advised. In 2000, the American Academy of Pediatrics recommended delaying the introduction of common allergenic foods such as milk to age 1 year, egg to age 2 years, and peanuts, nuts, and fish until age 3 years, Dr Sicherer explained.

"These recommendations were erased 8 years later because there wasn't really any evidence to support them, and in fact, there started to be increasing evidence that waiting longer and longer to introduce allergenic foods might actually pose risk," he said. Now, evidence supports much earlier introduction of allergenic foods, especially for infants at the highest risk for food allergy (namely, those with severe eczema or egg allergy), who are now believed to benefit from peanut exposure as early as 4 to 6 months of age. Such exposure prevents them from becoming allergic to peanuts, but not other allergenic foods, Dr Sicherer noted.

"In all cases, it's important for parents and everyone else to know that peanuts are a choking hazard for babies, as is peanut butter," he emphasized. "But safe forms of peanut in specific amounts are suggested," he observed. The writing group, in turn, found little evidence that elimination of allergenic foods by pregnant or lactating women prevents future food allergies in their infants.

Evidence supporting a protective effect of breast-feeding against future food allergies is also limited.

Emergency Management

Other important aspects of the summary document include the underuse of epinephrine to treat anaphylaxis, Dr Sicherer said. "Paper after paper after paper indicates that epinephrine is underutilized, that bad outcomes happen when it's not utilized appropriately, but that, when used promptly, epinephrine reduces the need for additional doses, it reduces hospitalization, and presumably also mortality. So people need to know epinephrine is safe."

Unfortunately, epinephrine autoinjectors come in only two strengths — 0.15 and 0.30 mg — doses that are really too high for infants, he added. The committee thus recommends industry develop an autoinjector that contains only 0.075 mg of the drug, which would be appropriate for infants. "It's hard for an outsider to understand that every single meal, snack, social activity, birthdays, Thanksgiving, holidays — everything is food, and it's very difficult to live with a serious food allergy," Dr Sicherer noted.

"So it takes a whole community to keep a child safe, and while it can start with the family and the physician, schools, camps, restaurant personnel, even people who work in emergency departments, all need to be educated, and it really is quite a daunting task," he concluded.

Dr Sicherer has disclosed no relevant financial relationships. One coauthor reports receiving grant support for pediatric nutrition research from food and pharmaceutical companies. Another coauthor received grant support for research from the National Institute of Food and Agriculture and from the Food Allergy Research and Resource Program consortium of more than 90 food manufacturers and/or suppliers, as well as royalties from Neogen Corp. Another coauthor reports being on the DBV Technologies scientific advisory board and receiving support for a pediatric allergy clinical trial's unit from the National Peanut Board, has received a discounted Bamba peanut snack from Osem, and has stock and/or stock options in DBV Technologies. The other authors have disclosed no relevant financial relationships.

Pediatrics. Published online July 24, 2017. Abstract

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