Bronchial challenge tests with direct and indirect stimuli – Which are more useful?

There is a large selection of bronchial challenge tests. The most commonly employed tests involve provocation with methacholine, histamine, exercise, a hypertonic saline solution, or mannitol. The first two mentioned tests use pharmacological substances acting directly on bronchial smooth muscles causing constriction and increased blood vessel permeability. The remaining tests are considered as indirect stimuli, which by osmotic mechanisms lead to release of endogenous mediators responsible for quick obturation of the respiratory tract. Studies in recent years concerning direct tests have shown interpretation discrepancies when using approved methods and tools to carry out the tests. Bronchial challenge tests with mannitol, which have greater specificity for asthma, are increasingly being promoted. However, negative results of these tests are frequently encountered in patients with well-controlled asthma which is not the case in tests involving methacholine.