What is the significance of eosinophilia in Chronic Obstructive Pulmonary Disease (COPD)?

From the Guidelines

Eosinophilia in COPD should be managed with inhaled corticosteroids (ICS) in combination with long-acting bronchodilators for patients with blood eosinophil counts ≥300 cells/μL or ≥2-3% of total white blood cells, as this subgroup is more likely to respond to ICS therapy and have reduced exacerbations 1.

Key Considerations

• Patients with eosinophilic COPD often show better response to ICS such as fluticasone, budesonide, or beclomethasone, which should be used in combination with long-acting bronchodilators like fluticasone/vilanterol, budesonide/formoterol, or beclomethasone/formoterol.
• For acute exacerbations in eosinophilic COPD, systemic corticosteroids like prednisone are particularly effective, typically prescribed at 40mg daily for 5-7 days.
• The biological basis for this treatment approach lies in the role eosinophils play in airway inflammation, which resembles patterns seen in asthma and responds similarly to corticosteroid therapy.
• Regular monitoring of blood eosinophil counts can help guide treatment decisions, particularly when considering whether to initiate, continue, or withdraw ICS therapy in COPD management.

Treatment Approach

• The 2023 Canadian Thoracic Society guideline on pharmacotherapy in patients with stable COPD recommends against stepping down from LAMA/LABA/ICS triple combination therapy to dual combination therapies for individuals at high risk of exacerbations, especially those with blood eosinophils counts ≥ 300 cells/mL 1.
• The guideline also suggests the addition of macrolide maintenance therapy or roflumilast/N-acetylcysteine for symptomatic individuals with impaired health status at high risk of AECOPD who continue to exacerbate despite being on LAMA/LABA/ICS triple combination therapy.

Evidence Base

• The evidence supporting the use of ICS in eosinophilic COPD is based on post-hoc analyses of clinical trials, which suggest that higher blood eosinophil counts may predict increased exacerbation rates in patients treated with LABAs without ICS, and that the treatment effect of ICS/LABA versus LABA on exacerbations is greater in patients with higher blood eosinophil counts 1.
• Prospective trials are required to validate the use of blood eosinophil counts to predict ICS effects and to determine a cutoff threshold for blood eosinophils that predicts exacerbation risk.

From the Research

Eosinophilia in COPD

• Eosinophilia is a potential biomarker for identifying patients with COPD who may benefit from inhaled corticosteroid (ICS) treatment 2, 3, 4.
• Studies have shown that patients with higher blood eosinophil counts tend to have a greater reduction in exacerbation rates with ICS therapy 2, 3, 4.
• A systematic review and meta-analysis found that a blood eosinophil count of ≥2% was associated with a greater reduction in COPD exacerbation rate and pneumonia incidence 4.
• Another study found that the proportion of patients with elevated eosinophil counts was higher in those with a history of ≥2 exacerbations, particularly in GOLD D patients 5.
• The role of blood eosinophils in the management of COPD is still being clarified, but they may represent a potential candidate surrogate marker for specific COPD patients 6.

Blood Eosinophil Counts and ICS Treatment

• A study found that patients with blood eosinophil counts <150 cells/μL did not benefit from continued ICS treatment, while those with counts ≥150 cells/μL had a significant reduction in exacerbation rates 2.
• Another study found that patients with ≥2% blood eosinophils had a significant reduction in exacerbation rates with ICS/LABA therapy, while those with <2% eosinophils did not 3.
• A meta-analysis found that the 2% threshold for blood eosinophils could accurately predict ICS treatment response in patients with COPD, but increased the risk of pneumonia 4.

Clinical Implications

• Blood eosinophil counts may be used to identify patients with COPD who are more likely to benefit from ICS treatment 2, 3, 4.
• The use of ICS-based therapy was found to be higher in GOLD D patients, but there was no apparent relation between ICS use and eosinophil blood count 5.
• Further research is needed to clarify the role of blood eosinophils in the management of COPD and to determine the optimal treatment strategies for patients with different blood eosinophil counts 6.