Screening tests, such as skin tests (SPT) and serum IgE levels can predict food allergic reactions but ultimately, feeding patients the suspected allergic food is the only way of confirming or ruling out a food allergy (oral food challenge).
Oral Food Challenges (click to enlarge the diagram).
The double-blind oral food challenge (OFC) is the best method from from research perspective but the procedure can take upwards of 8 hours and is often impractical in most real-life settings.
In a recent JACI article, data was reviewed from 700 oral challenges performed at a university-based pediatric allergy outpatient clinic (Mount Sinai School of Medicine, New York) during 2 years.
Patients were rarely challenged if the risk of reaction was deemed to be greater than 50%.
19% of the challenges were positive, i.e. elicited a reaction. Milk, peanut, wheat, and soy most commonly elicited a reaction.
Factors associated with positive challenges included:
- larger positive reaction on skin tests
- higher food-specific serum IgE levels
- 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 (88%) of reactions were treated with an antihistamine alone. Only 1.7% of all challenges required epinephrine.
Open OFC 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).
OCF is a relatively safe procedure with systemic reactions occurring at a rate that is equivalent to systemic reactions to "allergy shots."
There has been no reported death from oral food challenge done by a board-certified allergist in a supervised clinical setting. Please do not attempt an oral food challenge at home because of the risk of fatal reaction.
8 top allergens account for 90 percent of food allergies. Specific IgE levels (sIgE) that predict the likelihood of passing an oral food challenge are shown in the figure. (click to enlarge the image).
Comparison of diagnostic methods for peanut, egg, and milk allergy - skin prick test (SPT) vs. specific IgE (sIgE) (click to see the spreadsheet). Sensitivity of blood allergy testing is 25-30% lower than that of skin testing, based on comparative studies (CCJM 2011).
Outpatient open oral food challenges – feasible and “feed-able”. AAAAI.
Food Challenges for Diagnosis of Food Allergy
When to Attempt a Food Challenge in Tree Nut Allergy?
Comments from Twitter:
@allergistmommy: I've been doing more peanut OFC's lately, esp in concert with component resolved diagnostics.