RELATIONSHIP BETWEEN FOOD-SPECIFIC IGE CONCENTRATIONS AND THE RISK OFPOSITIVE FOOD CHALLENGES IN CHILDREN AND ADOLESCENTS

Background: The double-blind, placebo-controlled food challenge (DBPCF C) is the ''gold standard'' for diagnosis of food hypersensitivity: Sk in prick tests and RASTs are sensitive indicators of food-specific IgE antibodies but poor predictors of clinical reactivity. Previous studi es suggested that high concentrations of food-specific IgE antibody we re predictive of food-induced clinical symptoms, Because the CAP Syste m PEM (Pharmacia Diagnostics, Uppsala, Sweden) provides a quantitative assessment of allergen-specific IgE antibody, this study was undertak en to determine the potential utility of the CAP System FELA in diagno sis of IgE-mediated food hypersensitivity, Methods: Sera from 196 pati ents with food allergy were analyzed for specific IgE antibodies to eg g, milk, peanut, soy, wheat, and fish by CAP System FELA. Sera were ra ndomly selected from 300 stored samples of children and adolescents wh o had been evaluated by history, skin prick tests, and DBPCFCs. The st udy population was highly atopic: all patients had atopic dermatitis, and approximately 50% had asthma and allergic rhinitis at the time of initial evaluation, The performance characteristics of the CAP System FELA were compared with those of skin prick tests and the outcome of D BPCFCs or ''convincing'' histories of anaphylactic reactions, Results: The prevalence of specific food allergies in the study population var ied from 22% for wheat to 73% for egg, Allergy to egg, milli, peanut, and soy accounted for 87% of confirmed reactions, The performance char acteristics of skin prick tests and CAP System FEW (egg, milk, peanut, fish) were comparable, with excellent sensitivity and negative predic tive accuracy but poor specificity and positive predictive accuracy. T he performance characteristics of the CAP System FELA for soy and whea t were poor, For egg, milk, peanut, and fish allergy diagnostic levels of IgE, which could predict clinical reactivity in this population wi th greater than 95% certainty, were identified: egg, 6 kilounits of al lergen-specific IgE per liter (kU(A)/L); milk, 32 kU(A)/L; peanut, 15 kU(A)/L; and fish, 20 kU(A)/L. Conclusions: When compared with the out come of DBPCFCs, results of CAP System FELA are generally comparable t o those of skin prick tests in predicting symptomatic food hypersensit ivity. Furthermore, by measuring the concentrations of food-specific I gE antibodies with the CAP System FELA, it is possible to identify a s ubset of patients who are highly likely (>95%) to experience clinical reactions to egg, milk, peanut, or fish, This could eliminate the need to perform DBPCFCs in a significant number of patients suspected of h aving IgE-mediated food allergy.