Exhaled nitric oxide as a marker of airway inflammation for an epidemiologic study in schoolchildren

Background: Exhaled nitric oxide (eNO) levels are increased in airway inflammatory disorders, such as asthma. Objective: We sought to determine whether eNO could serve as a noninvasive marker of allergic airway inflammation for an epidemiologic study in schoolchildren. Methods: Two hundred seventy-eight schoolchildren aged 10 to 12 years answered a modified American Thoracic Society questionnaire, and eNO levels and pulmonary function were measured. In 246 subjects serum nonspecific IgE levels and levels of IgE specific to house dust mite, cat, cedar, and mold were also measured. Correlation analysis was used to examine eNO levels, nonspecific IgE levels, antigen-specific IgE levels, and pulmonary function. In addition, we compared these variables between subjects with (recurrent wheezers) and without (nonwheezers) recurrent wheeze. Finally, multiple logistic regression analysis was used to find possible predictors for recurrent wheezers. Results: eNO showed significant positive correlations with nonspecific IgE (r = 0.62, P < .001) and mite-specific IgE (r = 0.74, P < .001) and weak positive correlations with specific IgE to cat and cedar. Only eNO showed a weak but significant inverse correlation with pulmonary function (% FEV1, P = .035; FEV1/forced vital capacity, P = .018). eNO, nonspecific IgE, and mite-specific IgE levels in recurrent wheezers were greater (P < .001), and % FEV1 was less (P = .06) when compared with values seen in nonwheezers. Finally, eNO was determined by means of multiple logistic regression analysis to be the best predictor for recurrent wheezers compared with other variables (odds ratio, 11.2; 95% CI, 1.33-94.0). Conclusion: eNO can be used in epidemiologic studies as a noninvasive marker of allergic airway inflammation in schoolchildren.