Egg Allergen Specific IgE Diversity Predicts Resolution of Egg Allergy in the Population Cohort HealthNuts

Abstract

Egg allergy is one of the most common food allergies in children. Standard care for egg allergy involves assessing for tolerance to baked egg products. Egg white–specific immunoglobulin E has limitations for predicting tolerance to baked egg products. Researchers in this study investigated whether egg component-resolved diagnostic (CRD) technology could predict baked egg tolerance and development of tolerance to egg. Ovalbumin (Gal d 2) is the most abundant protein in egg white and is heat labile. Ovomucoid (Gal d 1) makes up a smaller percentage of protein in egg white but may be more significant because it is resistant to heating. The role of sensitization to Gal d 3 and egg yolk allergen Gal d 5 has not been well characterized.A subset of 451 subjects from the HealthNuts cohort were selected for this study. HealthNuts is a large population-based sample of 5276 Australian children recruited at age 1 year. Peanut and egg allergy were determined by oral food challenge.A total of 297 children with egg allergy had positive egg challenge results and were egg sensitized by a skin prick test (SPT) wheal >2 mm. This group was compared with 154 egg-tolerant children who passed egg challenge (57 had negative SPT results and 97 showed sensitization with an SPT wheal <2 mm). All children with egg allergy at 12 months of age were invited to participate in an additional baked egg oral food challenge. At 2 and 4 years of age, children with egg allergy had repeat egg challenge, SPTs, and specific immunoglobulin E (sIgE) tests (including CRD test for egg, which included Gal d 1, 2, 3, and 5 using ImmunoCAP). The association between egg allergen component sIgE and the risk of raw, baked, and persistent egg allergy was studied by generating the receiver operating characteristic (ROC) curve on the basis of sensitivities and specificities for a range of cutoff values for sIgE measurements. The area under the curve (AUC) along with 95% confidence intervals (CIs) were calculated.To determine egg allergy at 1 year of age, Gal d 1 sIgE and Gal d 2 sIgE provided ROC curves with AUC values of 0.83 (95% CI: 0.81–0.87) and 0.63 (95% CI: 0.60–0.67), respectively, whereas the AUC of egg white sIgE was 0.89 (95% CI: 0.85–0.92). To determine baked egg allergy at 1 year of age, sIgE to Gal d 1 and Gal d 2 provided ROC curves with AUC values of 0.65 (95% CI: 0.61–0.070) and 0.77 (95% CI: 0.73–0.81), respectively, whereas egg white sIgE generated an ROC curve with an AUC of 0.80 (95% CI: 0.76–0.84). Gal d 1 sensitization increased risk of persistent egg allergy by 2.5-fold. The presence of sIgE to all 4 egg allergens increased the risk of persistent egg allergy fourfold (95% CI: 1.25–14.07).Egg CRD testing offers no advantage over egg white sIgE for evaluating raw egg allergy and baked egg allergy at 1 year of age. Sensitization to multiple egg allergens Gal d 1, 2, 3, and 5 increases risk of persistent raw egg allergy.Baked egg challenges are frequently conducted when evaluating infants and young toddlers with egg allergy. Unfortunately, egg CRD testing does not appear to be any more helpful then egg white sIgE when selecting appropriate children for baked egg food challenges. There does not appear to be a role for routinely obtaining egg CRD testing when evaluating children with histories of adverse egg reactions.