Study: Inflammatory Biomarkers Helpful in Diagnosing Eosinophilic COPD

Inflammatory biomarkers, such as sputum eosinophilic percentage, fractional exhaled nitric oxide (FeNO) level, and blood eosinophilic percentage, can be used to diagnose eosinophilic chronic obstructive pulmonary disease (COPD), according to a recent study.

Although measurements of eosinophils in sputum and FeNO are used as noninvasive biomarkers for airway inflammation phenotypes in COPD, the clinical application of the correlation between FeNO levels and sputum eosinophilia is controversial.
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In order to investigate the predictive relationship between FeNO levels and sputum eosinophils in patients with COPD exacerbation, and the relationship between FeNO levels and blood eosinophil percentage, researchers conducted a cross-sectional study including 163 patients with COPD exacerbation. All patients underwent FeNO test, spirometry, bronchodilator reversibility test, induced sputum, and routine blood test, and were classified as either eosinophilic or noneosinophilic based on sputum eosinophilic percentage.

Overall, FeNO levels and blood eosinophilic percentage were higher in patients with sputum eosinophilia (n=62) compared with those without sputum eosinophilia, and sputum eosinophilic percentage was higher with raised FeNO compared with those with lower FeNO. Eosinophils in induced sputum correlated with FeNO levels and blood eosinophilic percentage, but there was no relationship between FeNO and blood eosinophilic percentage.

Blood eosinophilic percentage was predictive of sputum eosinophilia  at a cutoff point of 0.65%, and FeNO levels were predictive of sputum eosinophilia at a cutoff point of 17.5 parts per billion.

“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,” the researchers concluded.

—Michael Potts

Reference:

Gao J, Zhang M, Zhou L, et al. Correlation between fractional exhaled nitric oxide and sputum eosinophilia in exacerbations of COPD [published online April  27, 2017]. Int J Chron Obstruct Pulmon Dis. doi:https://doi.org/10.2147/COPD.S134998.