Utility of ovomucoid-specific IgE concentrations in predicting symptomatic egg allergy.

BACKGROUND Children with allergy to raw egg white might tolerate low amounts of heated egg. Ovomucoid-specific IgE antibodies have been suggested to be predictors of whether children could tolerate heat-treated egg. OBJECTIVE The aim was to evaluate the clinical usefulness and added diagnostic value of measurements of IgE antibodies to egg white, ovalbumin, and ovomucoid in children with egg allergy. METHODS One hundred eight patients (median age, 34.5 months) with suspected egg allergy underwent double-blind, placebo-controlled food challenges with raw and heated egg. The outcomes of the challenges were related to the serum concentration of specific IgE antibodies and total IgE by using ImmunoCAP. RESULTS Reactions to heated egg white were observed in 38 patients (considered allergic to raw and heated egg), 29 patients reacted to only raw egg white, and 41 patients were tolerant. Correlation was observed between the serologic parameters studied. Receiver operating characteristic analysis showed that egg white ImmunoCAP was useful in the diagnosis of allergy to raw egg white. The positive decision point, based on 95% clinical specificity, was 7.4 kU(A)/L, and the negative decision point, based on 95% clinical sensitivity, was 0.6 kU(A)/L. For reaction to heated egg white, ovomucoid ImmunoCAP was superior. The positive decision point was 10.8 kU(A)/L, and the negative decision point was 1.2 kU(A)/L. CONCLUSIONS Quantitative measurements of specific IgE antibodies to both egg white and ovomucoid and the evaluation against the suggested positive and negative decision points for specific IgE will be useful in the diagnosis of egg allergy.