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

Abstract

Asthma guidelines emphasize maintaining disease control. However, objective measures of asthma disease control are lacking. We sought to examine the relationship between exhaled nitric oxide (NO) levels and measures of asthma disease control versus asthma disease severity. We performed a cross-sectional study of 100 patients (age range, 7-80 years) with asthma. We administered a questionnaire to identify characteristics of asthma, performed spirometric testing before and after administration of a bronchodilator, and measured exhaled NO levels in all participants. Exhaled NO was significantly correlated with the following markers of asthma disease control: asthma symptoms within the past 2 weeks (P =.02), 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). Markers with relevance to both disease control and severity showed either a weak correlation (FEV(1) and FEV(1) percent predicted) or no correlation (controller drug use) with exhaled NO. 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.