Blood eosinophil count and risk of pneumonia hospitalisations in individuals with COPD

Abstract

Introduction: Blood eosinophil count in COPD is associated with higher exacerbation rate and favorable response to corticosteroids; however, frequent exacerbations and use of inhaled corticosteroids could also elevate pneumonia risk. We tested the hypothesis that high blood eosinophil counts are associated with high risk of pneumonia in individuals with severe COPD from the general population.

Methods: We included 7,180 individuals with COPD, including 643 with FEV₁<50% of the predicted value from the Copenhagen General Population Study, from 2003-2011. All primary discharge diagnoses of pneumonia during follow-up were recorded.

Results: Among individuals with COPD and FEV₁<50% of the predicted value, the multivariable adjusted incidence rate ratio was 2.17(95% confidence interval, 1.31–3.58) for pneumonia comparing individuals with blood eosinophil counts at or above versus below 0.34·10⁹/L. In individuals with clinical COPD, defined by recent exacerbation, ≥10 pack-years, and FEV₁<70% of the predicted value, the corresponding risk was 4.52(2.11–9.72). Risk of pneumonia did not differ by blood eosinophil count in individuals with COPD and FEV₁≥50% of the predicted value.

Conclusion: In individuals with COPD and FEV₁ below 50% percent of predicted value, blood eosinophil count of 0.34·10⁹/L or higher was associated with high risk of hospitalisation due to pneumonia.