The Usefulness of Blood Eosinophil Levels as Biomarkers for COPD Exacerbation Risk

This observational, multicenter study evaluated the reliability of blood eosinophil levels to determine the risk for exacerbation and responsiveness to inhaled corticosteroids (ICS) in patients with chronic obstructive pulmonary disease (COPD). The trial included patients in stable COPD with Gold Initiative for Chronic Obstructive Lung Disease airflow obstruction grades II to IV. The researchers defined concordance as blood eosinophil levels that were consistently lower or higher than the absolute cutoff points of 150 cells/μL and 300 cells/μL, or the percentage cutoff points of 2%, 3%, and 4%. Discordance was defined as variations in blood eosinophil values between any two visits. Data on ICS treatment responsiveness were recorded at a single time point. Final analysis included 210 patients (70% were male) with 2,059 visits. The average patient age was 67.7 ± 9.4 years, 36% were current smokers, and 81% were under ICS treatment at the beginning of the study. Eosinophil levels were evaluated over a median time of seven days (range, 4-12 days), regardless of exacerbation or hospitalization. At the 2%, 3%, and 4% cutoffs, the rates of discordance were 77%, 60%, and 42%, respectively. When only considering two visits, the prevalence of discordance at each cutoff was 34.5%, 24.0%, and 17.2%, respectively. Results were similar for discordance using absolute eosinophil values. Stable patients had higher discordant values compared with those with mild or moderate exacerbations; this also held true among patients hospitalized for other illnesses versus severe COPD exacerbation. Discordance was high, regardless of ICS treatment. The authors concluded that a single assessment of blood eosinophil levels may not be the best predictor of ICS response in patients with COPD. Read more