FeNO distribution and its relevant factors in the general adult population and its 'healthy' subpopulation

ABSTRUCT Background Measurement of fractional exhaled nitric oxide (FeNO) has been used in the diagnosis and management of asthma. Understanding the distribution of FeNO in a larger resident population and its 'healthy' subpopulation would contribute to the interpretation of FeNO in clinical practice. Objective This study aimed to investigate the distribution and its associated factors in the adult population and its 'healthy' subpopulations. Methods We conducted a cross-sectional study of 8,638 men and 17,288 women aged 20 years or older living in Miyagi Prefecture, Japan. We investigated the distribution of FeNO and its associated factors in all subjects, the subpopulation with no history of upper and lower airway diseases (healthy subpopulation 1), and the subpopulation with no history of upper and lower airway diseases, normal lung function, no positivity of other biomarkers of type 2 inflammation (healthy subpopulation 2). Results The distribution of FeNO in healthy subpopulations, especially in healthy subpopulation 2 (median [IQR]: 17[12-23] with 95th percentile of 36 ppb) was lower than in all subjects (19[13-26] ppb with 95th percentile of 47 ppb). In healthy subpopulation 1, 10.3 % had elevated FeNO (≥35 ppb) and elevated FeNO was positively associated with the factors including obstructive ventilatory defect, blood eosinophilia, positive for house dust mite-specific IgE and history of hypertension. Male gender was associated with elevated FeNO in all subjects and healthy subpopulations. Conclusion The distribution of FeNO in the 'healthy' subpopulation supports the validity of the criteria (≥35 ppb) currently used in Japan for the diagnosis of asthma.