Fractional Exhaled Nitric Oxide is Associated with the Severity of Stable COPD

The value of fractional exhaled nitric oxide (FeNO) in patients with chronic obstructive pulmonary disease (COPD) remains unclear. We aimed to assess whether FeNO is a more valuable biomarker than blood eosinophil count for identifying clinical characteristics of COPD. Stable COPD patients (n = 390) were included and stratified by FeNO and blood eosinophil counts at recruitment. The demographic characteristics, lung functions, St George Respiratory Questionnaire (SGRQ), serum inhaled allergen-specific IgE and the exacerbations in the preceding 12 months were compared. Risk factors for moderate or severe exacerbation in the preceding 12 months were examined by binary regression analysis. The cross-sectional study showed that 167 patients had high level of FeNO (≥25 ppb) and 223 in low level (