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 FEV(1), 85.7%) receiving short-acting inhaled bronchodilators and a range of inhaled steroids (0 to 4,000 microg/d).
Interventions: Subjects were studied on two occasions, 5 to 7 days apart, between September and March.
Measurements and results: On the first day, FEV(1), 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 FEV(1) or the provocative concentration causing a 20% fall in FEV(1). 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.