Clinical utility of fractional exhaled nitric oxide and blood eosinophils counts in the diagnosis of asthma-COPD overlap

Yusuke Takayama, Hiroshi Ohnishi, Fumiya Ogasawara, Kosuke Oyama, Tetsuya Kubota, Akihito Yokoyama Department of Hematology and Respiratory Medicine, Kochi Medical School, Kochi University, Nankoku City, Kochi, Japan Background: Asthma–COPD overlap (ACO) is difficult to diagnose because it is characterized by persistent airflow limitation, and patients present with several manifestations that are usually associated with both asthma and COPD. In this retrospective study, we aimed to evaluate the diagnostic accuracy of fractional exhaled nitric oxide (FeNO) and blood eosinophil counts for the clinical diagnosis of ACO.Patients and methods: A total of 121 patients were divided into two study groups, COPD alone or ACO, which was based on criteria from the joint document by the Global Initiative for Asthma and the Global initiative for chronic Obstructive Lung Disease. From July 2014 to April 2017, FeNO levels and blood eosinophil counts were measured in specimens from patients naïve to inhaled corticosteroids (ICS) and those using ICS. Receiver operating characteristic curve analysis was used to determine the cutoff values of FeNO and blood eosinophil levels that provided the best differential diagnosis between ACO and COPD.Results: Among a total of 121 patients, 65 patients were diagnosed with COPD and 56 patients with ACO. The FeNO level was higher in patients with ACO than in patients with COPD (median 24.5 vs 16.0 ppb, respectively; P