Food Allergen Panel Testing Often Results in Misdiagnosis of Food Allergy
April 14, 2015
Food allergies have become an increasing public health issue. Recent studies now indicate that nearly 1 in 13 children are diagnosed with food allergy. Food allergies are triggered when the immune system make a special type of antibody, called IgE, directed against foods. On re-exposure to the food, the IgE antibody can trigger severe, even life threatening allergic reactions.
The diagnosis of food allergy is typically done through a combination of a detailed medical history coupled with specific food allergy testing. Classically, such testing is through skin prick testing where a small amount of the food is applied to the skin and the skin is then pricked with a small sterile probe, allowing the liquid to seep under the skin. After about 20 minutes, a hive (a bump similar to a mosquito bite) may form indicating allergy. More recently, a blood based test commonly referred to as RAST or Immunocap testing has grown increasingly popular. Unfortunately, these blood based tests can be overly sensitive and have false positive results. This can lead to misdiagnosis of food allergy which leads to unnecessary food avoidance, unnecessary medication prescriptions, and increased cost.
In a recent study in Journal of Pediatrics, Bird and colleagues at the University of Texas Southwestern Medical Center and Dell Children’s Medical Center in Dallas reviewed the charts of 797 patients referred for evaluation of possible food allergy. They selected patients in whom the primary care provider had ordered a standard panel of food-specific IgE tests. Such a panel was done in 284 (35%) of all patients. Of these, only 90 patients (32.8%) had a history that warranted such testing.
Diets were altered in 126 of patients based on the initial testing. Of these, 72 did not have histories suggestive of food allergy and all of these individuals were found to not have food allergy. In total, 112 (88.9%) of the 126 patients who were avoiding foods were able to reintroduce at least one food. It was estimated that the cost associated with those patients whose history did not warrant food allergy testing was $79, 412.
The diagnosis of food allergy hinges on a detailed history and physical exam. Food-specific IgE testing is a vital tool used to confirm food allergy. This study, however, highlights that panels of food specific IgE tests have little utility as a screening tool. Such panels often result in the over-diagnosis of food allergy. A ‘positive’ test does not automatically translate into clinical food allergy, as a significant proportion of individuals with a positive test are not clinically allergic.
All Allergy Partners physicians are Board Certified Allergist-Immunologists. This means that they have undergone two to three years of specialized training in the diagnosis, treatment and management of allergic diseases, including food allergy. They have expertise in the interpretation of food allergy test results and are equipped to offer food challenges which are the definitive test for the diagnosis of food allergy. If you are concerned about food allergy, contact your Allergy Partners physician.
Source: Bird JA, Crain M, Varshney P. Food Allergen Panel Testing Often Results in Misdiagnosis of Food Allergy. J Pediatrics 2014:166(1):97-100.