Abstract

A direct stimulus such as methacholine is generally used to measure bronchial hyperresponsiveness. AMP, an indirect airway challenge, has been reported to be a better marker of inflammation than direct challenges and can be used in the differential diagnosis of asthma from other airway diseases. In this study, the effects of bronchial provocation test (BPT) using AMP and methacholine were compared in patients with asthma and COPD as well as healthy smokers and non-smokers. The study population consists of 60 subjects including 16 with mild asthma, 14 with mild-moderate COPD (8 current smokers and 6 ex-smokers), 15 non-smokers, and 15 current smokers. All the subjects underwent BPT using AMP and methacholine. 14 (87.5%) patients with asthma and seven (50%) patients with COPD were AMP responsive at a concentration of PC20≤100mg/ml (p=0.046). When asthmatic patients and current smokers with COPD were compared to each other, no significant difference was found related toAMP and methacholine responsiveness. However, one (16.7%) ex-smoker with COPD and 14 (87.5%) patients with asthma were AMP responsive at a concentration of PC20≤100mg/ml (p=0.004). Re-evaluated at an AMP concentration of PC20≤800mg/ml, 15 asthmatics (93.8%) and two ex-smokers with COPD (33.3%) were assessed to be hyperresponsiveness to AMP (p=0.009). Patients with COPD were more responsive to the maximal concentration of both AMP and methacholine than healthy smokers (p=0.008, p=0.009). Provocation test using AMP is more sensitive than methacholine in the differentiating diagnosis of airway inflammation in asthma and COPD and being a current smoker may increase inflammation, and thus the AMP responsiveness in COPD.