Using fractional exhaled nitric oxide level to differentiate asthma–COPD overlap syndrome from chronic obstructive pulmonary disease

Abstract

INTRODUCTION: Measurement of fractional exhaled nitric oxide (FeNO) is a simple, noninvasive, reproducible, and convenient method for assessing airway inflammation. We here assessed the value of FeNO for distinguishing asthma‑COPD overlap syndrome (ACOS) and chronic obstructive pulmonary disease (COPD) in patients hospitalized due to exacerbation of COPD.METHODS: A total of 100 consecutive patients diagnosed with COPD and hospitalized due to disease exacerbation were included and divided into the COPD‑alone group and ACOS group. FeNO was measured at the beginning of hospitalization and at discharge.RESULTS: There was no correlation between FeNO values measured at the time of hospitalization and hospital duration (r = −0.10, P = 0.334). However, the mean FeNO value at the beginning of hospitalization was significantly higher in the ACOS group than in the COPD‑alone group (25.5 [11–149] vs. 13.0 [5–50]; P < 0.001). The initial FeNO value was a good predictor of ACOS, with an optimumvalue of 18.5 parts per billion (sensitivity, 80%; specificity, 80%; positive and negative predictive values, 63.6% and 90.6%, respectively).CONCLUSION: The FeNO level can identify ACOS in patients hospitalized for COPD exacerbation, providing a new diagnostic tool for the clinical management of ACOS and COPD.