Bronchoprovocation tests in asthma

Airway hyperresponsiveness (AHR) is a characteristic feature of asthma, and its measurement using direct inhalation challenges, particularly with inhaled methacholine or histamine, or indirect challenges using stimuli such as exercise, dry air hyperpnea, distilled water, hypertonic saline and mannitol, and the pharmacological agent adenosine monophosphate is important in establishing a correct diagnosis. Direct challenge tests are sensitive and have a high negative predictive value to exclude asthma. This is particularly true in excluding asthma as a diagnosis in patients with symptoms that suggest asthma, but are caused by another condition. Indirect AHR correlates better with eosinophilic airway inflammation. Therefore, indirect challenge tests are seen as more specific. A newer indirect challenge test that uses a kit containing prepacked capsules of dry powder mannitol in different doses is safe and efficient to use. Indirect challenge tests are superior to direct challenge tests to confirm the presence of asthma.