SPT < 7mm and sIgE < 2kU/L identify children likely to tolerate peanut (only 5% likelihood of failing oral challenge)

A growing number of preschool children are identified as peanut sensitized in the course of investigation of other allergic conditions. But are they "truly allergic"? Although many have never ingested peanuts and their clinical reactivity is not known, it has been common practice to place these children on avoidance diets for many years.

This Australian study aimed to determine the utility of skin prick tests (SPT) and fluorescent-enzyme immunoassays (FEIA) for identifying either peanut allergy or tolerance in preschoolchildren with peanut sensitization.

49 preschool children (younger than 5 years of age) with peanut sensitization (defined as SPT larger than 2 mm or peanut-specific IgE greater than 0.35 kU/L) but unknown clinical reactivity had graded open peanut challenges reaching a total of 11 grams. A positive challenge was defined as an IgE-mediated reaction during challenge or the 2-h observation.

49% of children had positive challenges. An SPT greater than 7 mm on the day of challenge predicted a positive challenge with a sensitivity of 83% and a negative predictive value (NPV) of 84%.

sIgE greater than 2.0 kU/L showed a sensitivity of 79% and an NPV of 80%.

The tests worked much better when combined. Predicting challenge outcome from a combination of SPT and FEIA (SPT greater than 7 mm and/or FEIA  greater than 2) increased sensitivity to 96% and NPV to 95%.

At least half of preschool children with peanut sensitization and no history of peanut ingestion can tolerate peanuts.

A SPT less than 7 mm and FEIA less than 2 kU/L identify children most likely to tolerate peanut, with only a 5% likelihood of failing an oral challenge. This study would definitely help allergists when considering oral challenges in peanut-sensitized children.


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).

References:

Skin prick testing and peanut-specific IgE can predict peanut challenge outcomes in preschoolchildren with peanut sensitization. Johannsen H, Nolan R, Pascoe EM, Cuthbert P, Noble V, Corderoy T, Franzmann A, Loh R, Prescott SL. Clin Exp Allergy. 2011 Mar 24. doi: 10.1111/j.1365-2222.2011.03717.x.
Food Allergen Avoidance
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Image source: Roasted peanuts as snack food, Wikipedia, public domain.