Outpatient open oral food challenges – feasible and “feed-able”
Published Online: August 12, 2011
Inappropriate diagnosis of food allergy can lead to life-threatening reactions or unnecessary avoidance of foods and psychological distress. Screening tests, such as skin tests and serum IgE levels, can help predict reactions, but ultimately, feeding patients the suspected allergic food is the only way of confirming or ruling out a food allergy. The double-blind oral food challenge (OFC) is the accepted best method for doing this, but this procedure can take upwards of 8 hours and requires dedicated facilities to perform appropriately. Therefore, many physicians simply feed the suspected allergen to patients in an open, un-blinded challenge as a surrogate test; yet very few studies have examined this type of open challenge.
In a Letter to the Editor in The Journal of Allergy & Clinical Immunology (JACI), Lieberman et al. reported results from the largest series of open OFCs to date. They reviewed 22 months worth of successive open OFCs performed at a university-based pediatric allergy outpatient clinic (Mount Sinai School of Medicine, New York, NY). All patients were suspected of possible food allergy due to evidence of reaction history and/or positive allergy testing. Decisions to proceed with OFCs were made by the allergists in the clinic in conjunction with families’ interests on an individual basis; however, patients were rarely challenged if the risk of reaction was deemed to be greater than 50%.
The authors reported results of 701 challenges over the 22 month period. 18.8% of the challenges were positive, i.e. elicited a reaction. The challenged foods were common food allergens (in descending order of frequency: peanut, tree nuts, egg, milk, soy, fish, sesame, shellfish, wheat, and others). Milk, peanut, wheat, and soy most commonly elicited a reaction. Factors associated with positive challenges included larger skin tests, higher food-specific serum IgE levels, and history of past reaction to the food (as compared to those patients who were avoiding a food due to previous test results and had never eaten the food). The majority (87.9%) of reactions were treated with an antihistamine alone, while 12 reactions, or 1.7% of all challenges, required epinephrine.
The authors showed that the open OFC can be done in high volume, and can be very effective in adding foods back to the diets of the majority of patients, if selected when the testing and history are favorable (estimated less than 50% chance of reaction). This likely represents a majority of patients encountered in most pediatric allergy outpatient clinics. It is a relatively safe procedure as well, with systemic reactions occurring at a rate that is equivalent to or lower than most published studies on systemic reactions to allergy shots.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.