Workshop 4: The role of bronchoprovocation

Provocation tests can be used to investigate the effects of NBAAD. These studies provide scientific information on the pharmacology of drugs in humans, their potential clinical efficacy, and the optimum dose and duration of their effect. They serve as a useful link between preclinical studies and clinical trials; however, they do not necessarily identify the clinical value of drugs and they are not a substitute for clinical trials. Provocation tests include inhalation tests with chemical mediators of airway narrowing, tests with natural nonsensitizing stimuli such as exercise and hyperventilation, and inhalation tests with allergens. Each of these stimuli acts through different specific mechanisms. All of them can trigger early asthmatic responses; exercise can also stimulate late asthmatic responses; and allergens can induce late asthmatic responses and prolonged increases in airway responsiveness to chemical mediators. The provocation tests must be carefully regulated to produce reproducible responses against which the effect of the drugs can be examined. This stipulation requires that the patient, environment, stimulus, and airways measurements are the same for each treatment condition. The study design must incorporate the scientific principles applicable to all drug studies. While guidelines can be given to studies that involve tests with chemical mediators, exercise, and hyperventilation, they cannot yet be specified for allergen inhalation tests, for which the factors that influence reproducibility are less well understood.