Introduction:Eosinophils have a key role in the pathogenesis of COPD as a marker of therapeutic response to inhaled corticosteroids. Some studies indicate that eosinophils may have an immunoregulatory role related to the presence of emphysema. The aim of this study was to investigate the relationship between the presence of pulmonary emphysema and the blood eosinophil count (and percentage) in a COPD population.
Methods:patients from the COPD cohort of the Hospital de la Princesa (Madrid, Spain) were studied. Information about blood test, chest CT-scan and pulmonary function was analysed. The correlation between pulmonary function and blood eosinophil values (minimum, maximum, and average) was analyzed. Clinical variables, eosinophil values and lung function values were compared between COPD patients with radiological emphysema and COPD patients without emphysema.
Results:We studied 572 patients with COPD, of which 307 had emphysema by CT-scan. Statistically significant correlations were found, although clinically not very relevant between eosinophils and FEV1, DLCO and KCO (r2 0.067, 0.003, 0.052 respectively, p <0.05). Patients with radiological emphysema had lower body mass index, FEV1, DLCO, KCO and higher RV. No significant differences were found between eosinophil values when comparing the population with or without emphysema.
Conclusions: Eosinophilia in blood is not a good marker of the presence of emphysema in patients with COPD, so it is unlikely that eosinophils play a pathogenic role in this population. However, the presence of some weak correlations suggests that their role should be investigated in selected subpopulations.