Reference values and determinants of exhaled nitric oxide in healthy Korean adults.

BACKGROUND: Measuring fractional exhaled nitric oxide (FeNO) provides an indication of airway inflammation and is used as an inflammatory marker for asthma management. However, reference values and determinants of FeNO levels are not well defined in healthy Asian adults. This study aimed to establish FeNO reference values in nonsmoking, healthy Asian adults and to determine the factors related to FeNO levels.

METHODS: The authors measured FeNO in 166 nonsmoking, healthy Korean adults and collected data regarding factors possibly associated with FeNO, including age, height, weight, and respiratory symptoms. Lung function was measured using spirometry, and atopic status was determined based on the skin-prick test.

RESULTS: In a multivariate linear regression analysis, FeNO levels were positively associated with male gender (p = .008) and atopy (p = .044) after adjusting for age, height, weight, forced expiratory volume in one second (FEV(1)), and chronic rhinitis. Reference values were presented according to gender and atopic status, and the mean FeNO value was highest in male atopic subjects (37.3 +/- 12.1 ppb), followed by nonatopic males (33.9 +/- 14.3 ppb), atopic females (28.6 +/- 17.7 ppb), and nonatopic females (24.1 +/- 10.6 ppb). In healthy Korean adults, FeNO levels showed a significant and independent association with male gender and atopy.

CONCLUSIONS: We believe that the presented FeNO reference values and the determining factors could be useful for research and clinical practice in the adult Asian population.