Bronchial allergen challenge with isolated major allergens of Dermatophagoides pteronyssinus: the role of patient characteristics in the early asthmatic response.

BACKGROUND: The use of allergen extracts will hamper studies into quantitative aspects of allergic responses because the precise amount of relevant allergen for each patient is unknown. OBJECTIVE: We applied isolated IgE-binding components (major allergens) in the technique of bronchial allergen challenge to determine the role of patient characteristics in the early asthmatic response (EAR). METHODS: In 30 patients with mild-to-moderate asthma, the EAR was investigated after inhalation of an isolated major allergen of Dermatophagoides pteronyssinus (i.e., Der p 1 [n = 16] or Der p 2 [n = 14]). The degree of early-phase bronchial responsiveness to allergen (the cumulated dose of allergen causing a 20% fall in FEV1 [PD20allergen]) was related to the degree of nonspecific bronchial responsiveness (the concentration of histamine causing a 20% fall in FEV1 [PC20histamine]) and the level of specific IgE or allergen thresholds as found in skin tests and basophil histamine release assays. RESULTS: Twenty-seven patients with an immediate response during allergen and histamine challenges (deltaFEV1, > or = 20%) were analyzed. In these patients, a strong correlation was found between PD20allergen and PC20histamine (r = 0.81, p < 0.001). Weak correlations were found between PD20allergen and the level of specific IgE (r = -0.36, p = 0.07) or allergen thresholds as found in skin tests (skin prick test, r = 0.36 and p = 0.07; intracutaneous test, r = 0.49 and p = 0.01) or basophil histamine release assays (r = 0.37, p = 0.08). Moreover, no significant contribution of these indices of IgE-mediated hypersensitivity to the prediction of PD20allergen by multilinear regression models with PC20histamine was found. CONCLUSION: In asthmatic patients allergic to house dust mites the degree of nonspecific bronchial hyperresponsiveness is the main determinant of early-phase bronchial responsiveness to allergen. In these patients the degree of allergic sensitivity does not contribute to the prediction of the EAR after allergen inhalation.