Predictive value of eosinophils and neutrophils on clinical effects of ICS in COPD

Inflammation is present to a variable degree and composition in patients with COPD. This study investigates associations between both eosinophils and neutrophils in blood, sputum, airway wall biopsies and bronchoalveolar lavage (BAL) and their potential use as biomarkers for clinical response to inhaled corticosteroids (ICS).

In total, 114 steroid-naïve COPD patients of the Groningen Leiden Universities Corticosteroids in Obstructive Lung Disease (GLUCOLD) study using ICS or placebo during 30-month follow-up were included. Cell counts in blood, sputum, biopsies and BAL were evaluated at baseline. In addition, at baseline, 6 and 30 months, forced expiratory flow in 1 s (FEV₁ ), residual volume/total lung capacity (hyperinflation) and Clinical COPD Questionnaire were evaluated.

Cross-sectional analyses at baseline showed that higher blood eosinophils were significantly associated with higher eosinophil counts in sputum, biopsies and BAL. However, blood neutrophils did not significantly correlate with neutrophil counts in the other compartments. Baseline eosinophils and neutrophils, in whichever compartment measured, did not predict longitudinal FEV₁ changes. Higher baseline biopsy eosinophils were associated with an increase in symptoms during 6- and 30-month ICS treatment. In addition, higher biopsy neutrophils were associated with a more marked reduction in hyperinflation during 6-month ICS treatment compared with placebo.

Our findings indicate that blood eosinophils reflect eosinophils in other compartments, in contrast to neutrophils, in ICS-naïve COPD patients. Both baseline eosinophils and neutrophils do not predict ICS-induced lung function changes over a period of 6-30 months. The associations of biopsy eosinophils with worsening respiratory symptoms and biopsy neutrophils with improvement in hyperinflation during ICS treatment deserve further investigation.