Background: Blood eosinophil counts have been documented as a good biomarker for patients with chronic obstructive pulmonary disease (COPD) using inhaled corticosteroid (ICS) therapy. However, the effectiveness and safety of prescribing high or medium dose of ICS for patients with different eosinophil counts are unknown.
Methods: A post hoc analysis of a previous prospective randomized study was performed for COPD patients using higher dose (HD: Fluticasone 1,000 μg/day) or medium dose (MD: Fluticasone 500 μg/day) of ICS combined with Salmeterol (100 μg/day). Patients were classified into two groups: those with high eosinophil counts (HE ≥3%) and those with low eosinophil counts (LE <3%). Lung function was evaluated with forced expiratory volume in 1 second, forced vital capacity, and COPD assessment test. Frequencies of acute exacerbation and pneumonia were also measured.
Results: Two hundred and forty-eight patients were studied and classified into higher eosinophil (HE) (n=85, 34.3%) and lower eosinophil (LE) groups (n=163, 65.7%). The levels of forced expiratory volume in 1 second were significantly increased in patients of HE group treated with HD therapy, compared with the other groups (HE/HD: 125.9±27.2 mL vs HE/MD: 94.3±23.7 mL, vs LE/HD: 70.4±20.5 mL, vs LE/MD: 49.8±16.7 mL; P<0.05) at the end of the study. Quality of life (COPD assessment test) markedly improved in HE/HD group than in MD/LE group (HE/HD: 9±5 vs LE/MD: 16±7, P=0.02). The frequency of acute exacerbation was more decreased in HE/HD group patients, compared with that in LE/MD group (HE/HD: 13.5% vs LE/MD: 28.7%, P<0.01). Pneumonia incidence was similar in the treatment groups (HE/HD: 3.2%, HE/MD: 2.6%, LE/HD: 3.5%, LE/MD 2.8%; P=0.38).
Conclusion: The study results support using blood eosinophil counts as a biomarker of ICS response and show the benefits of greater improvement of lung function, quality of life, and decreased exacerbation frequency in COPD patients with blood eosinophil counts higher than 3%, especially treated with higher dose of ICS.
Keywords: blood eosinophil; chronic obstructive pulmonary disease; inhaled corticosteroid.