Influence of atopy on exhaled nitric oxide in patients with stable asthma and rhinitis

The level of exhaled NO is increased in patients with allergic asthma and seasonal rhinitis. The aim of this study was to investigate the significance of atopy on NO production in the lower airways. Measurements of exhaled NO were performed in 131 stable asthmatic patients with chronic mild asthma (95 atopics and 36 nonatopics), 72 patients with perennial rhinitis (57 atopics and 15 nonatopics) and 100 healthy controls (20 atopics and 80 non-atopics). Patients with either asthma or rhinitis had higher exhaled NO values (13.3+/-1.2 parts per billion (ppb) and 11.7+/-1.1 ppb) than control subjects (4.8+/-0.3 ppb, p<0.01). Exhaled NO levels were significantly higher in atopic asthmatics (19+/-3.6 ppb) compared with nonatopic patients (5.6+/-0.8 ppb, p<0.001). Similar findings were observed in patients with rhinitis (13.3+/-1.3 ppb in atopics and 5.8+/-1.2 ppb in nonatopics, p<0.001). No difference was found in NO levels between atopic and nonatopic control subjects (4.8+/-0.8 ppb, and 4.5+/-0.3 ppb). In summary, this study has shown that increased exhaled NO levels are detected only in atopic patients with asthma and/or rhinitis and not in nonatopic patients. These findings may suggest that it is rather the allergic nature of airways inflammation, which is mainly responsible for the higher NO production in the lower airways.