Most parents, and many physicians, do not understand the limitations of food allergy testing.  As I am sure is common among physicians, I frequently receive requests for food allergy testing; parents do not realize that the strategy for food allergy testing is not straight-forward and has not advanced significantly for decades.  This information is detailed in a recent study and associated editorial (J Pediatr 2015; 166: 97-100, editorial 8-10: “Pitfalls in Food Allergy”).

The study was a retrospective review of all new patients seen at a pediatric food allergy center (2011-2012).  This involved a review of 797 new patients.

Key findings:

• Of 284 patients who had received a food allergy panel, only 90 (32.8%) had a history warranting evaluation for food allergy.
• Among 126 individuals who had food restrictions imposed based on food allergy panel testing, 112 (88.9%) were able to re-introduce at least 1 food into their diet.
• The positive predictive value of food allergy testing was 2.2%.

So what can we learn from this study and editorial?

Misdiagnosis often relates to a lack of understanding regarding serum IgE-based testing.  First of all, many children with atopic dermatitis (and other atopic conditions) have elevated total IgE which results in more false positives.  In addition, a positive IgE test for a specific food indicates sensitization but not necessarily an allergy.

Strategy for testing (recommended by editorial):

• “The key to the diagnosis of food allergy cannot be overstated; it begins with a detailed clinical history”
• Testing should be “limited in general to the food(s) in question.”
• When there is uncertainty, oral food challenges can be performed by specialists.
• “If a patient is consuming a food without clinical symptoms of allergy, allergy testing should not be done to that food.”

Bottomline (from authors’ conclusion): “Food allergy panel testing often results in misdiagnosis of food allergy, overly restrictive dietary avoidance, and an unnecessary economic burden on the health system.”

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