Probability curves for predicting symptom severity during an oral food challenge with wheat.

Wheat allergy is the third most common food allergy among young children in Japan.1 The most reliable examination for the definitive diagnosis of a food allergy is an oral food challenge (OFC); however, consuming wheat appears to be an independent risk factor for anaphylaxis during OFC.2 As predictive factors for severe wheat OFC outcomes have not yet been identified, simple and easy indicators to predict induced symptom severity during wheat OFCs are needed. Omega-5 gliadin is a major allergen in young children with an immediate allergic reaction to wheat,3 and the serum u-5 gliadin-specific IgE level was reported to be a useful parameter for predicting positive OFC outcomes.4,5 Conversely, we previously reported probability curves for predicting symptom severity during egg and milk OFCs based on allergen-specific IgE levels6,7 to add clinical usefulness to these that only predict positive outcomes.1 Here we report probability curves for predicting symptom severity during a wheat OFC. In this study, unified OFC protocols with a single database system were used to conduct a total of 1679 OFCs at 14 institutions between October 2012 and May 2014. The indication for OFC was decided according to the Japanese guidelines for food allergy with their clinical history of food allergy and related specific IgE levels.1,8 Of 173 wheat OFC cases, 117 OFCs with sufficient data for patients aged 6 years were included in the final analysis. We excluded 56 cases including 4 older patients, 16 cases of insufficient dosing, 3 inconclusive cases, and 33 cases without appropriate specific IgE data. Udon noodles were used for wheat exposure; children ingested 1, 2, 5, 10, and 20 (or 30) g of udon noodles in increasing order at intervals of 15e30 min. Considering that udon noodles contain 3.1% wheat protein,8 the maximal total consumed wheat proteins was 1488 mg during OFCs. An OFC was terminated once a distinct allergic symptom was induced following ingestion. Severity of induced allergic symptoms was graded from 1 to 5 using the grading system of the guideline,1 which is based on Sampson's anaphylaxis severity score.9 In this study, a negative outcome was defined as the consumption of at least 38 g of udon noodles without any induced symptoms.8 Serum u-5 gliadinand wheat-specific IgE levels were monitored for 3 months prior to OFCs using the ImmunoCap test (Thermo Fisher Scientific, Uppsala, Sweden). The present study was approved by a local research ethics committee. In statistical analyses, allergen-specific IgE levels, which were out of detection limits, were considered as 0.17 kUA/L for levels