Blood Eosinophils as Biomarkers to Drive Treatment Choices in Asthma and COPD

摘要

Background: Asthma and COPD are complex, heterogeneous conditions comprising awide range of phenotypes, some of which are refractory to currently available treatments. Elucidationof these phenotypes and identification of biomarkers with which to recognize them and guide appropriatetreatment remain a priority.Objective: This review describes the utility of blood eosinophils as a surrogate biomarker of eosinophilicairway inflammation, a common feature of specific asthma and COPD phenotypes. The role ofblood eosinophils in airway disease is described, as is their relevance in reflecting airway eosinophilia.Each disease is discussed separately as the manner in which blood eosinophils might be used as biomarkersdiffers. Focusing on patients with severe disease (persistent eosinophilic asthma and exacerbatingCOPD), we evaluate evidence examining eosinophils as biomarkers.Results: In asthma, the rationale for using blood eosinophils to guide treatment is clearly defined,backed by prospective, well-controlled studies. Higher eosinophil counts identify patients with moresevere disease and poorer outcomes, patients for whom biologic therapies targeting allergic and/oreosinophilic pathways are recommended. In COPD, the evidence is less robust. High blood eosinophilcounts are a modest predictor of future exacerbations, and may predict a favourable response to ICSon top of LABA/LAMA, especially in patients with a history of frequent exacerbations.Conclusion: Before extensive application in clinical practice, further evaluation of these findings inprospective clinical studies, and standardization of the appropriate thresholds of clinically relevanteosinophilia are needed, together with establishing whether single or multiple measurements are requiredin different clinical settings.