Investigating fractional exhaled nitric oxide (FeNO) in chronic obstructive pulmonary disease (COPD) and asthma–COPD overlap (ACO): a scoping review protocol

INTRODUCTION During the last decade, many articles have been published, including reviews on fractional exhaled nitric oxide (FeNO) use and utility in clinical practice and for monitoring and identifying eosinophilic airway inflammation, especially in asthma, and evaluating corticosteroid responsiveness. However, the exact role of FeNO in patients with chronic obstructive pulmonary disease (COPD) and its ability to distinguish patients with COPD and those having concomitant asthma, that is, asthma-COPD overlap (ACO) is still unclear and needs to be defined. Due to the broad topics of FeNO in chronic airway disease, we undertook a scoping review. The present article describes the protocol of a scoping review of peer-reviewed published literature specific to FeNO in COPD/ACO over the last decade. METHODS AND ANALYSIS We used Joanna Briggs Institute Reviewers' Manual scoping review methodology as well as Levac et al's and Arksey et al's framework as guides. We searched a variety of databases, including Medline, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Library, Web of Science, and BioSciences Information Service (BIOSIS) on 29 June 2016. Additional studies will be recognised by exploring the reference list of identified eligible studies. Screening of eligible studies will be independently performed by two reviewers and any disagreement will be solved by the third reviewer. We will analyse the gathered data from article bibliographies and abstracts. ETHICS AND DISSEMINATION To investigate the body of published studies regarding the role of FeNO in patients with COPD and its usefulness in the clinical setting, a scoping review can be used as a modern and pioneer model, which does not need ethics approval. By this review, new insights for conducting new research specific to FeNO in COPD/ACO population will emerge. The results of this study will be reported in the scientific meetings and conferences, which aim to provide information to the clinicians, primary care providers and basic science researchers.