Unscrambling Egg Allergy: The Diagnostic Value of Specific IgE Concentrations and Skin Prick Tests for Ovomucoid and Egg White in the Management of Children with Hen’s Egg Allergy

Resolution of egg allergy occurs in the majority of egg allergic children. Positive specific IgE antibodies to ovomucoid (OVM) have been suggested to be of greater predictive value for persistent egg allergy than specific IgE to egg white. The performance of OVM-specific IgE antibody levels in a cohort of children referred for a routine egg challenge was compared with egg white specific IgE levels in predicting a positive egg challenge. 24/47 subjects had persistent egg allergy. Receiver operating characteristic analysis showed that OVM-specific IgE testing was the most useful test for the diagnosis of persistent egg allergy. The optimal decision points for the prediction of persistent egg allergy were >0.35？ k U A / L for specific IgE levels to both EW and OVM, and ≥3？mm for SPT. Children with specific IgE levels suggestive of persistent egg allergy need not be subject to an egg provocation challenge, reducing both costs and risks to the child. 1. Introduction Egg allergy is common in early childhood, affecting 1-2% of all preschool children and may be associated with severe symptoms, including anaphylaxis [1–3]. Although remission of type 1 hypersensitivity to hen egg occurs in the majority of cases, hypersensitivity may persist through adolescence into adulthood, in which 12% of food allergies are attributed to egg [4–9]. Resolution of egg allergy may first manifest with tolerance to cooked egg products despite continued reaction to raw egg, whilst in others, allergy may persist to egg in any form [10–12]. The ubiquitous inclusion of egg in prepared foods as a result of its useful functional properties—including binding and emulsifying—renders complete egg avoidance difficult. The sooner tolerance to egg is ascertained, the sooner a child can enjoy a normal, unrestricted diet. This alleviates the social and emotional burden associated with having a food allergy and is important for normal growth and development [13]. Children with any form of egg allergy also need to be identified for vaccination purposes as both seasonal and pandemic influenza vaccines and yellow fever vaccine are contraindicated. The gold standard for the diagnosis of egg allergy is the double-blind placebo-controlled food challenge (DBPCFC) which is both resource and time expensive, and potentially hazardous [10, 14]. Routine skin prick and specific IgE antibody tests to whole egg white are of limited value and have poor sensitivity for the identification of children with allergy to raw egg. Many potentially allergenic egg proteins exist; the major recognized allergens being