The Peanut Story -From NEJM Blog

If you listen to any news source over the last day, there is a buzz about a new study regarding early peanut exposure in the prevention of peanut allergy.  A link to a blog that summarizes the study and the associated editorial:  NEJM Blog -Peanut Consumption in Infants For those who prefer a 1 minute video summary: Here’s a brief excerpt: The Learning Early About Peanut Allergy (LEAP) study, now published in NEJM, was a randomized, open-label, single-center study designed to compare two strategies to prevent peanut allergy: consumption or avoidance of peanuts. The trial enrolled children 4-11 months of age who were thought to be at high risk for developing a peanut allergy based on a history of severe eczema or egg allergy.  Participants were given a skin prick test to evaluate for sensitivity to peanut.  Children with a negative skin prick result (meaning no measureable skin wheal) or moderately positive (1-4mm wheal) were included in the study; children with a highly positive result (wheal >4mm) were excluded.  Infants were then stratified based on their skin prick test results. 530 infants in the skin prick test negative group and 98 infants in the skin prick test positive group were randomly assigned to either consume 6g of peanut protein per week or to avoid peanuts.  The primary outcome was the proportion of participants with a peanut allergy at age 5, determined by response to an oral peanut protein challenge. The results were impressive:  in the negative skin prick test group, the prevalence of peanut allergy at age 5 was 13.7% in the avoidance group versus 1.9% in the consumption group (P<0.001).  In the positive skin prick test group, 35.3% of those who avoided peanuts were allergic as compared with 10.6% of the consumption group (P=0.004).

This study (NEJM 2015; 372: 803-13) showed that the early introduction of peanuts (median age 7.8 months) significantly decreased the frequency of the development of peanut allergy among children at high risk for this allergy.  These results will result in changes in practice recommendations.  It is noted that approximately 10% of children who had a wheal of more than 4 mm develop after skin-prick testing were excluded.  The associated editorial (pages 875-77) by Rebecca Gruchalla and Hugh Sampson recommends a cautious approach: “any infant between 4 months and 8 months of age believed to be at risk for peanut allergy should undergo skin-prick testing for peanut. If the results are negative, the child should be started on a diet that includes 2 g of peanut protein three times a week for at least three years.” For those with mild positivity, “the child should undergo a food challenge…by a physician who has experience performing a food challenge.”

What is the Role for Allergy Testing in Eosinophilic Esophagitis?

A recent review article (Clin Gastroenterol Hepatol 2014; 12: 1216-23) summarizes the potential role of allergy testing for eosinophilic esophagitis (EoE).

The article summarizes the potential ways to use various allergy testing and reviews the literature on its effectiveness.  The article notes a couple of key points:

  • Overall, using skin prick testing (SPT) and atopy patch testing (APT), allergy testing has not proved more reliable then empirically administering a 6-food elimination diet.  Thus, “the issue remains whether food allergy testing provides a useful tool in EoE.” However, targeted testing-based diets (especially in children) may require elimination of fewer foods.
  • “Serum IgE food-specific IgE panels should not be used for EoE.”  “Testing for foods, especially IgE testing, leads to recognition of food sensitizations that may not be clinically relevant and that on elimination, could result in the loss of tolerance to the food.”
  • Testing for milk allergy is noted have a high false negative rate.
  • IgG based testing is not recommended.  In fact, IgG immunoglobulins are “associated with tolerance rather than allergy.”
  • “Only 8% of children will become tolerant to all foods that cause their EoE.”

Bottomline: While foods commonly triggers EoE, the tests to identify these foods are far from perfect. I find that families are quite uninformed about the frequent lack of correlation between allergy testing and true EoE triggers.

Related blog posts:

Summary of article: GI & Hepatology News August 2014 Role of Allergy Testing in EoE