Atopy influences exhaled nitric oxide levels in adult asthmatics

Study objective: To examine whether atopy influences exhaled nitric oxide (NO) levels in adults with established asthma. Setting: Specialist respiratory unit in a university teaching hospital. Patients: Twenty-eight asthmatics (mean FEV1, 85.7%) receiving short-acting inhaled bronchodilators and a range of inhaled steroids (0 to 4,000 mug/d). Interventions: Subjects were studied on two occasions, 5 to 7 days apart, between September and March. Measurements and results: On the first day, FEV1, exhaled NO, and histamine challenge were performed. On the second day, exhaled NO, total IgE, and skin-prick testing to six common allergens were conducted. Exhaled NO was measured with the single exhalation method. We found exhaled NO levels to correlate positively with total IgE (r = 0.43, p = 0.02) and number of positive skin-prick tests (p = 0.002). By contrast, there was no significant correlation between exhaled NO and FEV1 or the provocative concentration causing a 20% fall in FEV1. Subanalyses of steroid-treated and steroid-naive patients in this group revealed the same findings. Conclusion: Exhaled NO levels in asthmatics correlate more closely with atopy than with bronchial hyperreactivity and lung function.