Using Historical Blood Eosinophil Counts to Guide Treatment Decisions in Patients With Chronic Obstructive Pulmonary Disease.

BackgroundUp to 40% of patients with chronic obstructive pulmonary disease (COPD) have evidence of elevated eosinophil counts ≥ 300 cells/μL at some point during their disease. Blood eosinophil counts (BECs) are a biomarker that can identify patients with COPD and type 2 inflammation who are candidates for add-on inhaled corticosteroids (ICS) or biologic therapy. Evidence from real-world and clinical trial data shows variation in BECs over time in patients with COPD and type 2 inflammation.ObjectiveIn this article, we discuss factors that can influence eosinophil counts, how the use of historical eosinophil counts can inform treatment decisions, and practical considerations for identifying underlying type 2 inflammation in patients with COPD in the clinic.Expert opinion and conclusionsCurrently, there is no consensus on what constitutes "low" or "high" BEC in COPD or the frequency or number of eosinophil measurements needed to effectively guide disease management. Based on our experience from the clinic and available literature, we propose four broad phenotypic groups of patients with COPD: those with BEC predominantly ≥ 300 cells/μL, intermittently ≥ 300 cells/μL, within an intermediate range of 100 to 300 cells/μL, and those with BEC predominantly < 100 cells/μL. Identifying these patterns can help with more precise stratification for pharmacological interventions, such as adding ICS or biologic therapies. While single BEC measurements are easy to obtain and often sufficient to identify patients with COPD and high levels of type 2 inflammation, when interpreted alongside clinical characteristics, repeated BECs may be able to support a more personalized approach to COPD care.