What is the methacholine provocation test?
During methacholine provocation test, the examinee performs repetitive spirometry tests before and after the inhalation of increasing concentrations of methacholine (a bronchoconstrictor substance). Methacholine is able to cause bronchial spasm and reduce bronchial diameter. In patients with bronchial hyperresponsiveness, methacholine inhalation may cause drop in the spirometric indices as recorded with repeated spirometry tests .
This artificial deterioration of lung function is reversed after inhalation of salbutamol (a rapid-acting bronchodilator). The methacholine provocation test helps diagnose bronchial hyperresponsiveness, one of the main features of bronchial asthma and can be used where the diagnosis of asthma is in doubt.