Threshold levels in food challenge and specific IgE in patients with egg allergy: Is there a relationship?

Background: Previously published articles described a relationship between food-specific IgE and the outcome of food challenge in children with egg allergy. These investigations defined different levels of predictive values in different study populations and thus pointed toward the possibility of a certain level of specific IgE to egg white predicting a positive outcome in food challenge. Objective: The purpose of this study was to determine the utility of specific IgE in estimating threshold level to predict a positive outcome in food challenge. Methods: Fifty-six children were evaluated for egg allergy by titrated oral challenges. Sera were analyzed for specific IgE to egg white in 56 patients by using the Magic Lite test and 32 of 56 patients also by the CAP test. Values of specific IgE to egg white were compared to the outcome of challenges and the threshold level. Results: The diagnostic level of specific IgE predicting clinical reactivity in this population with greater than 95% certainty was identified as 10.8 standardized units/mL (Magic Lite) and 1.5 kilounits of allergen-specific lgE/L (CAP), respectively. We found no significant relationship between the specific IgE concentration (egg white) and the challenge threshold level. Conclusion: Although the specific IgE concentration correlated to a positive outcome in food challenge, there was no significant relationship between the quantification of specific IgE and the challenge threshold level. Therefore the standardized food challenge still remains the gold standard in the diagnosis of food allergy.