Bronchial Allergen Challenge Using the Medicaid Dosimeter

Background: Bronchial allergen provocations are well established in asthma research. We evaluated the reproducibility of single-concentration, single-step allergen challenges in volunteers with grass pollen allergy. Methods: Forty-seven subjects underwent bronchial challenges using the aerosol provocation system nebulizer (Medicaid Side-stream) with incremental doses of grass pollen to define the individual allergen dose that causes a 20% drop in FEV1 (PD20FEV1). In 39 subjects this procedure was followed by single-step challenges. Early and late asthmatic responses were monitored, and increases in exhaled nitric oxide were measured before and 24 h after single-step challenges. Results: After the first single-step challenge, the maximum drop in FEV1 was 21.3% +/- 8.0. A comparison of the drop in FEV1 to the initial incremental challenge (29.7% +/- 7.5) revealed an intraclass correlation of -0.30 (p<0.05). In the second single-step challenge, the mean drop in FEV1 was 20.9% +/- 7.2. Compared with the first single-step challenge, the intraclass correlation was 0.37 (p<0.05) and the 95% limits of agreement according to Bland and Altman were -17.5 to 18.1%. The increases in exhaled nitric oxide revealed substantial agreement in repeated single-step challenges (26.8 ppb +/- 27.8 and 21.8 ppb +/- 21.9, ICC 0.62, p<0.001). Conclusions: The use of aerosol provocation system to calculate the PD20FEV1 allergen is a timesaving procedure and is less prone to errors because only one dilution of the allergen is used. The repeatability in well-defined subjects is excellent to study the mechanisms of allergen-induced airway inflammation and the development of new treatments for allergic diseases. Copyright (C) 2011 S. Karger AG, Basel