Role of FeNO in predicting the responsiveness of inhaled corticosteroids in COPD: a systematic review

Abstract

BACKGROUND: Fractional exhaled nitric oxide (FeNO) as a predictor of inhaled corticosteroid (ICS) response in asthma has been established. However, the same has not been established in chronic obstructive pulmonary disease (COPD). An optimal value of FeNO for prescribing and monitoring ICS response has not been quantified. AIM: To examine the evidence for this association. METHOD: A systematic review was conducted of randomised controlled trials and observational studies examining the association between FeNO level and response to ICS in COPD patients. All studies examining this association were included. Five databases were searched thoroughly. Systematic screening, full-text reviews, and data extraction were carried out based on eligibility criteria. RESULTS: A total of 8690 studies were identified, 342 texts were screened fully, and six studies were included for the final review. One was a randomised controlled trial and the other five were non-randomised interventional trials. One study was conducted in asthma-COPD overlap (ACO patients). After ICS use, three studies found statistically significant correlations between FeNO and lung function improvement (FEV1), and three studies also found significant correlations between FeNO and COPD quality-of-life scores. CONCLUSION: Measurement of FeNO is non-invasive and standardised, with results available at the point of testing. Because of the small sample size and short duration of studies, exacerbation frequencies were not measured. Despite this, the review suggests that FeNO may be a potential biomarker for assessing ICS response in COPD. Further research that stratifies patients by FeNO levels and assesses the impact on acute exacerbations is needed to understand its potential value in routine clinical practice.