Blood Eosinophils as a Biomarker in Patients with COPD

Eosinophils in COPD 

In patients with COPD, raised eosinophil levels in the blood are associated with higher eosinophil levels in the lungs, which is a biomarker of type 2 inflammatory activity in the airway.¹ It has been found that up to 37% of COPD patients show indication of type 2 inflammation.^2-5 

• Link to Role of Type 2 Inflammation in COPD 

Raised blood eosinophil levels are detectable by ordering a complete blood count with differential. A large population-based study (N=39,824) evaluated the stability of blood eosinophilia over time. The stability of the blood eosinophil count was observed to be higher in patients with COPD with baseline counts <340 cells/µL vs ≥340 cells/µL. The findings from this study extend the understanding of blood eosinophil as a potential biomarker.⁵  

Raised blood eosinophil count in COPD is associated with poor clinical outcomes and increased healthcare cost 

Raised blood eosinophil count in COPD increased the risk of exacerbation,⁶ 1-year COPD-related readmission,⁷ and severe exacerbations⁸ as shown in the illustration below: 

COPD exacerbation risk increases with higher eosinophil counts. In the COPDGene study, COPD patients with blood eosinophil count ≥300 cells/μL demonstrated an increased risk of exacerbations. This was prospectively validated in the ECLIPSE study.⁶

Type 2 inflammation in COPD (Eosinophilic COPD) and its risks 

Raised blood eosinophils are associated with higher emergency department visits, outpatient visits, numbers of prescriptions* and increased rate of lung function decline.^9,10 Raised eosinophils in COPD may also lead to increased risk of 1-year COPD-related readmission, decreased time to first COPD-related readmission and increased number of 1-year COPD-related Emergency Department (ED) visits⁷ as shown in the illustration and table below:  

Risks associated with raised blood eosinophil levels 

To learn more about the impact of raised eosinophiles in COPD read this article 

An Overview of the impact of Type 2 Inflammation in COPD: Insights from Dr. Surya Bhatt 

Impact of blood eosinophil count in COPD on management decisions 

Initial pharmacological management (Group E^†)¹: 

GOLD references suggest that ICS should be added to long-acting bronchodilators therapy in patients with high blood eosinophils counts (≥300 cells/µL). Consider triple therapy (LABA+LAMA+ICS) if eosinophil count is ≥300 cells/μL and this is based on the effect of ICS on exacerbation prevention correlated to blood eosinophil count. There is no direct data on initiation with triple therapy in newly diagnosed patients. However, available studies in treated patients provide a rationale to initiate treatment with triple therapy in patients with high eosinophils counts (≥300 cells/µL).¹ 

Blood eosinophil count impact on initial management decisions, according to GOLD references¹ 

Follow-up pharmacological management: 

Exacerbations:¹  

GOLD references recommend escalation to LABA + LAMA for patients with persistent exacerbations on bronchodilator therapy. 

ICS is suggested to be added to LABA + LAMA in patients who develop further exacerbations. Beneficial response of ICS may be observed at blood eosinophil counts of ≥100 cells/μL. 

For patients treated with LABA + LAMA + ICS or those with eosinophil counts of <100 cells/μL who still have exacerbations — Please refer to GOLD guidelines for more information 

Blood eosinophil count impact on follow-up pharmalogical management decisions, according to GOLD¹ 

*Regardless of inhaled therapy 

†Group “E” are patients with frequent exacerbations (defined as ≥2 in the past 12 months or 1 exacerbation requiring hospitalization). 

COPD, chronic obstructive pulmonary disease; ED, emergency department; FEV1, forced expiratory volume in first second; GOLD, Global Initiative for Chronic Obstructive Lung Disease; HR, hazard ratio; ICS, inhaled corticosteroid; LABA, long-acting β2-agonist; LAMA, long-acting muscarinic antagonist; OR, odds ratio; IRR, incidence rate ratio; ULN, upper limit of normal.