Relationship between Methacholine Challenge Testing and exhaled nitric oxide in adult patients with suspected bronchial asthma.

Usually, hyperresponsiveness to inhaled methacholine is considered closely associated with a diagnosis of bronchial asthma. Recently, it has been clearly pointed out that bronchial hyperreactivity (BHR) is not a constant feature of asthma and that this condition is not always related to airways inflammation. In the present study we evaluated 42 Patients (21 positive and 21 negative for bronchial hyperreactivity, BHR) with the aim to determine the effect of Methacholine Challenge Testing (MCT) on the levels of exhaled nitric oxide (NO). Higher FeNO levels were found before methacholine provocation in the group that eventually resulted positive to the challenge, while after the challenge in both groups FeNO decreased in similar way, with no statistical difference. These data confirm that MCT is a relevant test for asthma diagnosis, but it is not always related to the severity of bronchial inflammation, while FeNO levels in our study have limited clinical significance when evaluated out of asthma exacerbation.