Short-term and long-term variation in bronchial response to histamine in asthmatic patients.

Standardized histamine provocations were repeated during remission on 10 atopic bronchial asthmatics, at 14 days (short-term) and after more than 12 months (long-term). During the survey, anti-asthmatic medication was not regularly used. For constructing dose-response curves, four doses of histamine (concentration range 0.015-8 mg/ml) were given at each provocation. Two-fold increasing concentrations of histamine solutions were nebulized and inhaled by tidal volume breathing for 2 min at 5 min intervals. When repeated within 14 days, the coefficient of variation, calculated from maximum fall in FEV1, was 23%. The individual range for similar fall in FEV1 was estimated to 0-1 dose-step. When repeated after more than one year, the corresponding coefficient of variation was 26%, the individual range for similar fall in FEV1 being 0-2 dose-steps. It is concluded that the individual variation in bronchial response to standardized histamine challenge in patients with atopic asthma during remission is small during a period of one to two years.