Eosinophilic versus non-eosinophilic COPD cannot be distinguished by lung function nor CT determined emphysema or airway remodelling

Abstract

COPD is characterised by chronic inflammation which is predominantly neutrophilic, but is eosinophilic in 10-40% of cases. Whether clinical features of COPD including an airway predominant versus emphysema phenotype are different between eosinophilic and non-eosinophilic COPD is unclear.

The EvA consortium recruited 458 subjects of which 412 had an assessable quantitative computed tomography (qCT) to determine lung density (Perc15Hu) and wall area % (WA%) of the apical segment of the right upper lobe. Other investigations conducted included lung function tests, blood and sputum samples, which were assessable in 256 subjects. The subjects were dichotomised into two groups using clinically important cut-offs for blood eosinophils (≥ 200 cells/mL; N=188) and percentage eosinophils in sputum (≥3%; N=111).

There were no significant differences between those subjects with or without eosinophilic COPD with respect to demographics, spirometry, lung volumes or diffusion. Total serum IgE was correlated with blood eosinophil counts (rs=0.233; p<0.0001), but not sputum eosinophils. There was no significant difference in lung density nor WA% between eosinophilic and non-eosinophilic COPD and no significant correlations between CT lung density and blood and sputum eosinophil counts (r=0.0639; p=0.210 and r=-0.0931; p=0.169 respectively) and %WA (r=-0.0125; p=0.802 and r=0.0914; p=0.164).

In conclusion, eosinophilic and non-eosinophilic COPD have similar clinical and physiological characteristics and cannot be distinguished by qCT-derived measures of emphysema or airway remodelling.