Development of a standardized methodology for double-blind, placebo-controlled food challenge in patients with brittle asthma and perceived food intolerance

Objective To develop a standardized, double-blind, placebo-controlled, food challenge (DBPCFC) methodology for identifying food intolerance in patient s with brittle asthma. Subjects/setting Patients with brittle asthma and perceived food intoleranc e were studied in hospital. Design Each of 3 protocols began with 5 days of dietary exclusion. Protocol 1 consisted of open food challenges in 29 patients, protocol 2 consisted o f 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 r adioallergosorbent tests and skin prick tests were conducted. A standard pa nel of hyperallergenic foods were masked in a soup (developed specially for this study) for every food challenge. Peak expiratory flow, forced expirat ory volume, and symptoms were assessed as objective measures of response. O pen food challenges at home followed each protocol. Each protocol took appr oximately 14 days in the hospital and 4 to 6 months at home. Results For protocols 1, 2 and 3, positive reactions were experienced by 52 %, 55%, and 66% of patients, respectively. Radioallergosorbent tests and sk in prick tests were shown to have 40% and 71% sensitivity, respectively, an d 74% and 77% specificity for predicting a positive food challenge. Applications/conclusions The high prevalence of food intolerance in patient s with brittle asthma was confirmed, as was the poor positive predictive va lue of skin prick tests and radioallergosorbent tests. The food challenge m ethod developed enables standardized identification of food intolerances in patients with brittle asthma and may be useful in other groups.