Role of Specific IgE and Skin Prick Testing in Predicting Food Challenge Results to Heated Egg

Abstract

Previous studies suggest that children with egg allergy may be able to tolerate baked egg. Reliable predictors of a successful baked egg challenge are not well established. We examined egg white–specific IgE levels, skin-prick test (SPT) results, and age as predictors of baked egg oral food challenge (OFC) outcomes. We conducted a retrospective chart review of children, aged 2–18 years, receiving an egg white–specific IgE level, SPT, and OFC to baked egg from 2008 to 2010. Fifty-two oral baked egg challenges were conducted. Of the 52 challenges, 83% (n 43) passed and 17% (n 9) failed, including 2 having anaphylaxis. Median SPT wheal size was 12 mm (range, 0–35 mm) for passed challenges and 17 mm (range, 10–30 mm) for failed challenges (p 0.091). The negative predictive value for passing the OFC was 100% (9 of 9) if SPT wheal size was 10 mm. Median egg white–specific IgE was 2.02 kU/L (range, 0.35–13.00 kU/L) for passed challenges and 1.52 kU/L (range, 0.51–6.10 kU/L) for failed challenges (p 0.660). Receiver operating characteristic (ROC) curve analysis for SPT revealed an area under the curve (AUC) of 0.64. ROC curve analysis for egg white–specific IgE revealed an AUC of 0.63. There was no significant difference in age between patients who failed and those who passed (median 8.8 years versus 7.0 years; p 0.721). Based on our sample, SPT, egg white–specific IgE and age are not good predictors of passing a baked egg challenge. However, there was a trend for more predictability with SPT wheal size. (Allergy Asthma Proc 33:275–281, 2012; doi: 10.2500/aap.2012.33.3544) E allergy is one of the most common food allergies in infants and young children with an estimated prevalence between 0.5 and 2.5%. A standard diagnostic approach includes a thorough clinical history in combination with skin-prick testing (SPT) and foodspecific IgE values to egg white. Treatment recommendations have included strict avoidance of egg, including baked products containing egg, with the theory that even minute ingestions could provoke symptoms or even delay natural resolution of the egg allergy. Another theory suggests that the early introduction of foods may induce tolerance. It has recently been reported that many children with egg allergy may actually be able to tolerate heated or baked egg. The mechanism for heated egg tolerance is related to egg proteins being denatured during the heating process, thereby, diminishing the allergenicity. Predictors of tolerance to baked egg may improve quality of life in food-allergic children because baked egg is found in so many foods. Retrospective and prospective studies have now reported that 55–93% of children with egg allergy are able to tolerate baked egg without reaction. Furthermore, recent studies suggest that regular consumption of baked egg products may actually hasten the natural resolution of egg allergy and even show a reduction in egg SPT size after heated egg is introduced into an egg-allergic individual’s diet. However, given that some egg-allergic individuals do not tolerate baked egg, establishing predictors for baked egg oral food challenge (OFC) outcomes will be clinically useful in identifying egg-allergic individuals who may tolerate baked egg. Physician-supervised OFCs remain the gold standard for food allergy diagnosis. In this study, we examined SPT results, food-specific IgE values, and age as predictors of baked egg OFC outcomes.