Exhaled nitric oxide levels correlate with measures of disease control in asthma

Background: Asthma guidelines emphasize maintaining disease control. Howeve r, objective measures of asthma disease control are lacking. Objective: We sought to examine the relationship between exhaled nitric oxide (NO) levels and measures of asthma disease control versus asthma disease severity. Methods: We performed a cross-sectional study of 100 patients (age range, 7 -80 years) with asthma. We administered a questionnaire to identify charact eristics of asthma, performed spirometric testing before and after administ ration of a bronchodilator, and measured exhaled NO levels in all participa nts. Results: Exhaled NO was significantly correlated with the Following markers of asthma disease control: asthma symptoms within the past 2 weeks (P = .0 2), dyspnea score (P = .02), daily use of rescue medications (P = .01), and reversibility of airflow obstruction (P = .02), Exhaled NO levels were not correlated with the following markers of asthma disease severity: history of respiratory failure (P = .20), health care use (P = .08), fixed airflow obstruction (P = .91), or a validated asthma severity score (P = .19), Mark ers with relevance to both disease control and severity showed either a wea k correlation (FEV1 and FEV1 percent predicted) or no correlation (controll er drug use) with exhaled NO, Conclusion: We conclude that exhaled NO levels are correlated predominantly with markers of asthma control rather than asthma severity. Monitoring of exhaled NO may be useful in outpatient asthma management.