Development of a Standardized Methodology for Double-blind, Placebo-controlled Food Challenge Patients with Brittle Asthma and Perceived Food Intolerance

To develop a standardized, double-blind, placebo-controlled, food challenge (DBPCFC) methodology for identifying food intolerance in patients with brittle asthma.Patients with brittle asthma and perceived food intolerance were studied in hospital.Each of 3 protocols began with 5 days of dietary exclusion. Protocol 1 consisted of open food challenges in 29 patients, protocol 2 consisted of 2 daily DBPCFCs in 22 patients, and protocol 3 involved 1 daily DBPCFC in 18 patients. Total immunoglobulin E level was measured and food-specific radioallergosorbent tests and skin prick tests were conducted. A standard panel of hyperallergenic foods were masked in a soup (developed specially for this study) for every food challenge. Peak expiratory flow, forced expiratory volume, and symptoms were assessed as objective measures of response. Open food challenges at home followed each protocol. Each protocol took approximately 14 days in the hospital and 4 to 6 months at home.For protocols 1, 2 and 3, positive reactions were experienced by 52%, 55%, and 66% of patients, respectively. Radioallergosorbent tests and skin prick tests were shown to have 40% and 71% sensitivity, respectively, and 74% and 77% specificity for predicting a positive food challenge.The high prevalence of food intolerance in patients with brittle asthma was confirmed, as was the poor positive predictive value of skin prick tests and radioallergosorbent tests. The food challenge method developed enables standardized identification of food intolerances in patients with brittle asthma and may be useful in other groups.