Chronic obstructive pulmonary disease (COPD) is a heterogeneous inflammatory lung disease. It is important to identify patients who would respond to anti-inflammatory treatment. This prospective study aims to determine how inflammatory biomarkers could be used to predict the potential effect of inhaled corticosteroids (ICS) in terms of symptoms and lung function. 　We evaluated the levels of blood eosinophils, exhaled nitric oxide fraction at a flow rate of 50mL/s (FeNO), alveolar nitric oxide concentration (Calv), immunoglobulin E and atopy in 43 patients with symptomatic COPD and correlated these expression levels with the changes in the COPD Assessment Test (CAT) and lung function by 12 weeks of add-on therapy with ciclesonide 400µg/day on bronchodilators. 　The mean changes in the CAT score and FEV1 were -1.4 points and +90 mL, respectively, with significant variation in the levels of change. The area under the receiver’s operating characteristic curve (AUC) for FeNO in predicting improvements in both the CAT score and FEV1 was 0.92. The AUC for Calv and blood eosinophils was 0.82 and 0.65. Two cutoffs were chosen, one corresponding to a high value of FeNO associated with certainty for response inclusion (FeNO=35 ppb; sensitivity=0.67, specificity=0.94; positive predictive value=0.80) and the other with certainty for response exclusion (FeNO=20 ppb; sensitivity=1.00, specificity=0.58, negative predictive value=1.00). Baseline FeNO values were significantly correlated with changes in FEV1 and CAT (all p<0.0001). 　FeNO could be a valuable biomarker for identifying individuals who respond to steroid therapy among patients with symptomatic COPD in terms of symptoms and airflow limitation. 　The study was prospectively registered with the University Hospital Medical Information Network (UMIN) in Japan (protocol ID 000010711).
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