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

Abstract

Background: Asthma and COPD are complex, heterogeneous conditions comprising a wide range of phenotypes, some of which are refractory to currently available treatments. Elucidation of these phenotypes and identification of biomarkers with which to recognize them and guide appropriate treat-ment remain a priority.Objective: This review describes the utility of blood eosinophils as a surrogate biomarker of eosinophilic airway inflammation, a common feature of specific asthma and COPD phenotypes. The role of blood 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 biomarkers differs. Focusing on patients with severe disease (persistent eosinophilic asthma and exacerbating COPD), 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 more se-vere disease and poorer outcomes, patients for whom biologic therapies targeting allergic and/or eosino-philic pathways are recommended. In COPD, the evidence is less robust. High blood eosinophil counts are a modest predictor of future exacerbations, and may predict a favourable response to ICS on 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 in pro-spective clinical studies, and standardization of the appropriate thresholds of clinically relevant eosino-philia are needed, together with establishing whether single or multiple measurements are required in dif-ferent clinical settings

<p>Predictive Value of Exhaled Nitric Oxide and Blood Eosinophil Count in the Assessment of Airway Eosinophilia in COPD</p>

“…Although the utility of blood eosinophils in the management of COPD patients, in particular, to guide the use of inhaled corticosteroid (ICS) therapy for exacerbation prevention has been extensively investigated in recent years, 8,9 the evidence for a relationship between local (airway) and systemic (blood) eosinophilia remains contradictory. 12,13 We have shown here that the number of eosinophils in the blood is a good indicator of airway eosinophilia in stable COPD patients but not in those with an ongoing exacerbation where the sensitivity of the test was poor (20-40%).…”

“…In recent years both peripheral blood eosinophil count 8,9 and fractional exhaled nitric oxide (F E NO 50 ) level 10,11 have been implicated as surrogate biomarkers to determine and quantify the degree of airway eosinophilia in COPD patients.…”

Clinical and laboratory characteristics of SARS-CoV2-infected paediatric patients in Jordan: serial RT-PCR testing until discharge

“…Normal laboratory values were based on the Harriet Lane Pediatric Handbook [14]. For the eosinophil count, <0.01 × 10 9 /L was considered eosinopenia, and a count of ≥ 0.3 × 10 9 /L was considered to be elevated platelets [15].…”

Suppressor of Variegation 3-9 Homologue 1 Impairment and Neutrophil-skewed Systemic Inflammation Are Associated with Comorbidities in COPD

“…Although nonspeci c in ammation and the Th1 response have been generally recognized as the major sources of in ammation in COPD, Th2 effector eosinophils are also implicated in some patients. Eosinophilic COPD, which is de ned using peripheral blood eosinophils as a practical biomarker, is a generally accepted treatable trait that is responsive to inhaled corticosteroids (5). Recent meta-analyses (6) have clearly demonstrated a continuous relationship between ICS prescription and a reduced exacerbation risk at variable thresholds, con rming the biomarker role of blood eosinophils.…”

“…Nevertheless, anti-IL5 or anti-IL-5 receptor monoclonal antibodies have failed to demonstrate consistent effects on patients with high blood eosinophil counts (7). Blood eosinophils are also associated with a trend towards an increased risk of exacerbation, with either a positive relationship or no relationship (5). Interestingly, in the Hokkaido COPD Cohort Study, subjects with blood eosinophilia had signi cantly slower annual FEV1 decline rates (8).…”