Clinical context critical in food allergy diagnosis

Tests for allergen-specific immunoglobulin E (IgE) performed by in vitro assays or skin testing identify a sensitized state and may identify triggers to be eliminated and help guide treatment. The results, however, must be selected and interpreted in the context of the medical history and knowledge of the epidemiology and immunology of food allergies, said Scott H. Sicherer, MD, the Elliot and Roslyn Jaffe Professor of Pediatrics, Allergy and Immunology, Jaffe Food Allergy Institute, Icahn School of Medicine at Mount Sinai Hospital, New York.

In a session on Saturday, October 11, titled “Understanding and applying the newest guidelines for food allergy,” he presented case histories to illustrate various issues in the diagnosis and management of food allergies.

It is important to understand IgE- and non–IgE-mediated food allergies and to differentiate them from intolerance, which “allows for more effective diagnosis and management,” he added. Emerging tests, including some now available (eg, testing for IgE binding to specific proteins in peanuts) can improve the diagnosis of food allergies by evaluating whether the immune response is directed toward labile “innocent” proteins or stable ones that are associated with allergic reactions.

Sicherer cautioned that a positive test does not, in isolation, diagnose a food allergy. Children who test positive often have no clinical illness when exposed to the allergen. On the other hand, a negative test does not necessarily rule out a diagnosis of food allergy, especially when a food allergy history is convincing. In these cases, a medically supervised oral food challenge may be necessary.

Current guidelines no longer suggest extensive periods of avoiding common allergens, such as peanuts, eggs, and milk, for otherwise healthy but allergy-prone infants. When a specific trigger is identified, avoidance of the causal food is the primary means of treatment. Detailed education and consideration of nutritional issues is important. In the case of an anaphylactic reaction, prompt administration of epinephrine is key in management, Sicherer added. -Karen Rosenberg