Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Apr 27:12:1287-1293.
doi: 10.2147/COPD.S134998. eCollection 2017.

Correlation between fractional exhaled nitric oxide and sputum eosinophilia in exacerbations of COPD

Jie Gao  1 , Min Zhang  2 , Liqin Zhou  1 , Xing Yang  1 , Haigui Wu  1 , Jianfang Zhang  1 , Feng Wu  1
Affiliations

Correlation between fractional exhaled nitric oxide and sputum eosinophilia in exacerbations of COPD

Jie Gao et al. Int J Chron Obstruct Pulmon Dis. .

Abstract

Introduction: Measurements of eosinophils in induced sputum and fractional exhaled nitric oxide (FeNO) are noninvasive biomarkers for assessing airway inflammation phenotypes in chronic obstructive pulmonary disease (COPD). Nevertheless, the clinical application of the correlation between FeNO levels and sputum eosinophilia is controversial. The study aimed to investigate the correlation and predictive relationship between FeNO levels and sputum eosinophils in patients with COPD exacerbation. It also examined the relationship between FeNO levels and blood eosinophil percentage.

Methods: A total of 163 patients with COPD exacerbation were included in the cross-sectional study. All patients underwent the following on the same day: FeNO test, spirometry, bronchodilator reversibility test, induced sputum, and routine blood test. They were classified as eosinophilic group or noneosinophilic group based on sputum eosinophilic percentage (≥2.5%)/FeNO levels (≥32 parts per billion [ppb]).

Results: FeNO levels and blood eosinophilic percentage were higher in patients with sputum eosinophilia (n=62) compared to those without (31.35 ppb versus 21.43 ppb, P=0.015; 2.71% versus 0.98%, P<0.0001, respectively). Sputum eosinophilic percentage was higher with raised FeNO (n=34) compared to those with FeNO <32 ppb (5.12% versus 3.12%, P=0.007). Eosinophils in induced sputum correlated with both FeNO levels (ρ=0.221, P=0.005) and blood eosinophilic percentage (ρ=0.399, P<0.001). There was no relationship between FeNO and blood eosinophilic percentage. Blood eosinophilic percentage was predictive of sputum eosinophilia (95% confidence interval [CI] =0.65-0.81, P<0.001) at a cutoff point of 0.65% (sensitivity =73%, specificity =61.3%). FeNO levels were predictive of sputum eosinophilia (95% CI =0.53-3,071, P=0.012) at a cutoff point of 17.5 ppb (sensitivity =65.1%, specificity =56.4%).

Conclusion: The clinical relevance of this study provides evidence that inflammatory biomarkers, including sputum eosinophilic percentage, FeNO level, and blood eosinophilic percentage, can be used to positively diagnose eosinophilic COPD. The FeNO level and blood eosinophilic counts/percentage, which determine an optimal cutoff for sputum eosinophilia, need more studies.

Keywords: blood eosinophil percentage; chronic obstructive pulmonary disease; eosinophils in induced sputum; fractional exhaled nitric oxide.

PubMed Disclaimer

Conflict of interest statement

Disclosure The author reports no conflicts of interest in this work.

Figures

Figure 1
Figure 1
Scatter plots for correlations among FeNO levels, eosinophilic percentage in induced sputum, and eosinophilic percentage in peripheral blood. Notes: (A) Correlation between percentage sputum eosinophils and FeNO levels (ppb). (B) Correlation between percentage sputum eosinophils and percentage blood eosinophils. Abbreviations: FeNO, fractional exhaled nitric oxide; ppb, parts per billion.
Figure 2
Figure 2
Receiver operating characteristic (ROC) curve for FeNO level and blood eosinophilic percentage to predict sputum eosinophilia (≥2.5%). Abbreviation: FeNO, fractional exhaled nitric oxide.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Eltboli O, Brightling CE. Eosinophils as diagnostic tools in chronic lung disease. Expert Rev Respir Med. 2013;7(1):33–42. - PubMed
    1. Brightling CE, Bleecker ER, Panettieri RA, Jr, et al. Benralizumab for chronic obstructive pulmonary disease and sputum eosinophilia: a randomised, double-blind, placebo-controlled, phase 2a study. Lancet Respir Med. 2014;2(11):891–901. - PMC - PubMed
    1. Eltboli O, Bafadhel M, Hollins F, et al. COPD exacerbation severity and frequency is associated with impaired macrophage efferocytosis of eosinophils. BMC Pulm Med. 2014;9(14):112. - PMC - PubMed
    1. Donohue JF, Herje N, Crater G, Rickard K. Characterization of airway inflammation in patients with COPD using fractional exhaled nitric oxide levels: a pilot study. Int J Chron Obstruct Pulmon Dis. 2014;16(9):745–751. - PMC - PubMed
    1. The Global Strategy for the Diagnosis, Management and Prevention of COPD [webpage on the Internet] Global Initiative for Chronic Obstructive Lung Disease (GOLD); 2017. [Accessed October 16, 2016]. Available from: http://www.goldcopd.org/

MeSH terms