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

Authors Takayama Y, Ohnishi H, Ogasawara F, Oyama K, Kubota T, Yokoyama A

Received 9 March 2018

Accepted for publication 2 June 2018

Published 21 August 2018 Volume 2018:13 Pages 2525—2532

DOI https://doi.org/10.2147/COPD.S167600

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Colin Mak

Peer reviewer comments 2

Editor who approved publication: Dr Richard Russell


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<0.01). Among patients naïve to ICS, the area under the receiver operating characteristic curve of FeNO values was 0.726, and the optimal diagnostic cutoff level of FeNO was 25.0 ppb, with 60.6% sensitivity and 87.7% specificity for differentiating ACO from COPD. FeNO (≥25.0 ppb) combined with blood eosinophil counts (≥250/µL) showed 96.1% specificity.
Conclusion: These results demonstrate that the FeNO level combined with blood eosinophil count is useful for the differential diagnosis between ACO and COPD.

Keywords: asthma–COPD overlap, fractional exhaled nitric oxide, blood eosinophil counts

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