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Assessment of the role of fractional exhaled nitric oxide in the diagnosis of asthma–chronic obstructive pulmonary disease overlap

Introduction Bronchial asthma and chronic obstructive pulmonary disease (COPD) are airway diseases with different etiology and a different presentation. Sometimes, asthma and COPD are present within the same patient as asthma–COPD overlap syndrome (ACOS). Aim To assess the role of fractional exhaled nitric oxide (FeNO) in the diagnosis of ACOS. Patients and methods A total of 60 patients with newly diagnosed stable COPD (n=20), bronchial asthma (n=20), and ACOS (n=20) were included from May 2016 to May 2017. COPD, asthma, and ACOS diagnosis depended on clinical history and examination and spirometric criteria according to GINA guidelines (2015). FeNO was measured and compared between the studied patients groups. The cutoff value for FeNO which can help in differentiating ACOS from COPD was determined. Results In the current study, the level of FeNO was significantly higher in the studied patients with ACOS in comparison with patients with COPD alone, and FeNO had significant positive correlation with sputum eosinophils % in patients with ACOS (P=0.013). Moreover, this study showed that the cutoff value of FeNO to differentiate ACOS from COPD was 20 parts per billion (with 80% sensitivity and 85% specificity and area under the curve=0.84). Conclusion This study showed that the measurement of FeNO can be used for early differentiation of ACOS from COPD alone for helping their proper management as early as possible.