MILK-SPECIFIC IMMUNOGLOBULIN E/TOTAL IMMUNOGLOBULIN E RATIO AS A PREDICTOR OF POSITIVE ORAL FOOD CHALLENGES IN CHILDREN WITH ALLERGY TO COW'S MILK

Abstract

INTRODUCTION: Skin-prick test wheal size and serum-specific immunoglobulin E (IgE) levels are able to predict, to an extent, the presence of allergy to certain foods. Nevertheless, the predictive value of these markers is not enough to substitute for oral food challenges, which suggests the need for improvement. OBJECTIVE: The goal was to determine the prognostic value of specific IgE/total IgE (tIgE) ratio in patients with allergy to cow's milk by using receiver operating characteristic (ROC) analysis. METHODS: Thirty-four open challenges were performed in children with a mean age of 18.4 months (range: 10.3–69.2 months) who had a previously diagnosed IgE-mediated allergy to cow's milk to reintroduce milk into their diet. Specific IgE levels, assessed by ImmunoCAP fluorescence enzyme immunoassay (Pharmacia Corp, Bridgewater, NJ), were obtained, and skin-prick tests were performed just before the challenge. The specific IgE (f2)/tIgE ratio was evaluated as a potential predictor of a positive challenge and compared with f2 alone by using ROC analysis. RESULTS: Of 34 challenges, 6 (17.6%) results were positive. Prechallenge milk-specific IgE levels and the f2/tIgE ratio were significant predictors (Pf2 = .007; Pratio = .008) of a positive challenge outcome. After ROC analysis, f2 provided a discrimination (between positive and negative provocations) of 0.8601 (ROC area under the curve); however, the f2/tIgE ratio provided a significantly greater discrimination of 0.9464. Values of the f2/tIgE ratio that are >0.1121 provide a 100% diagnostic accuracy (probability of a positive provocation result). CONCLUSIONS: The f2/tIgE ratio may be a novel, promising predictor of positive oral food-challenge results and should be evaluated prospectively in a larger sample.