The role of food allergy testing in the evaluation and treatment of patients with eosinophilic esophagitis is not yet clear, according to a study by Dr. Seema Sharma Aceves.

The report appears in the August issue of Clinical Gastroenterology and Hepatology (doi: org/10.1016/j.cgh.2013.09.007).

An argument in favor of food allergy testing is that patients will not have to avoid so many foods when their own individual triggers are identified.

Current data suggest, but do not definitively establish, that testing for food allergies is a reasonable approach for beginning to construct an elimination diet in children with EOE, but the data are inadequate to support that strategy in adults with the disorder, she said.

It is clear that food antigens function as triggers that both induce EOE in the first place and also exacerbate the condition once it is established. And removing food antigens from the diet resolves EOE, improving both endoscopic and histologic features, in more than 60% of adults and children.

But most large studies of food elimination diets have involved only children. "This type of large cohort data does not currently exist for the adult population, and smaller studies have not demonstrated success rates that mirror the pediatric data," Dr. Aceves said.

There are several reasons why an empiric elimination diet, which simply removes the six most allergenic food types from the diet, can actually be superior to testing each patient for the specific food types that trigger his or her EOE and then removing only those items from the diet.

First, simply removing these six food types – dairy, egg, soy, wheat, peanuts/tree nuts, and fish/shellfish – usually induces the same response rate as does the more complicated process of food allergy testing. It also spares patients the anxiety and discomfort of testing.

Second, testing for milk allergy notoriously yields a high rate of false-negative results.

Third, food-specific IgE can be caused by cross-reactivity with environmental allergens. For example, a patient with a respiratory allergy to grass can test positive for food allergy to wheat. In general, EOE patients are highly atopic and tend to be sensitized to multiple food and aeroallergens, she said.

And lastly, food allergy testing may reveal a food trigger but doesn’t address the need to perform endoscopy and biopsy after suspected triggers are eliminated from the diet and after they are eventually reintroduced, said Dr. Aceves of the division of allergy and immunology at Rady Children’s Hospital, San Diego.

An argument in favor of food allergy testing is that patients will not have to avoid so many foods when their own individual triggers are identified. In one study of children, those placed on an empiric elimination diet had to eliminate eight entire food groups, with numerous different foods falling under the general categories of peanuts/tree nuts and fish/shellfish. In contrast, children who eliminated only those items identified on testing had to eliminate an average of three food groups.

Food elimination diets "should be applied judiciously" because there is always the risk that patients will lose their tolerance for a food when it has been avoided for a long period of time. Sometimes patients are sensitized to a food but tolerate it because they have very low but steady exposures that allow the body to adapt to it. When that food is completely eliminated for a period of time and then reintroduced, it can trigger a severe allergic reaction and anaphylaxis.

Before reintroducing an allergenic food that has been eliminated from the diet, gastroenterologists may want to test first for a possible hypersensitivity reaction. Alternatively, the food can be reintroduced in a controlled setting such as an allergist’s office, where the staff can recognize and respond to anaphylaxis, and the necessary medications and equipment are readily available, Dr. Aceves said.

Some diagnostic tools that have recently become available for food allergy testing but have not yet been systematically assessed for identifying food triggers in EOE may eventually prove useful. These include peptide microarrays that gauge the repertoire of IgE in patient serum, component-resolved diagnostic testing that assesses which epitopes within a food antigen are recognized by patient serum, and assays that analyze either the release or the activation of basophils in the periphery.

Finally, the recent finding that food-specific, CD4-positive, IL-5-producing T cells can be found in the peripheral blood is intriguing, Dr. Aceves said. If these cells are found to exist in the esophagus as well, then assays for such peripheral T cells might also function as markers for EOE food triggers.

This work was supported by the National Institute of Allergy and Infectious Diseases. Dr. Aceves reported no financial conflicts of interest.

Role of food allergy testing in EOE unclear