Eosinophilic Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease's eosinophilic phenotype: Clinical characteristics, biomarkers and biotherapy

COPD is a chronic, heterogeneous inflammatory disorder of the airways with persistent and poorly reversible airflow limitation, causing symptoms such as cough, shortness of breath, and sputum production. Despite optimal treatment, some patients remain symptomatic due to the disease's heterogeneity, manifesting in various phenotypes. One notable phenotype involves eosinophilic inflammation, with a variable prevalence. Identifying eosinophilic phenotypes is crucial for tailored therapeutic strategies, as they respond favorably to corticosteroids and potentially biologics. Recent advances in both clinical trials and spontaneous research have helped understand the biological and clinical characteristics of this phenotype, although no universal consensus has been reached yet on the definition of the cut-off values of the eosinophil peripheral blood count. Moreover, there is evidence of novel emerging biomarkers which might go beyond the sole eosinophil count, while significant advancements in terms of pharmacological treatment have been made, with dupilumab being the first biological drug being licensed for COPD patients with elevated circulating eosinophils in the stable phase. In light of the above, although several papers have been written on the relationship between eosinophils and COPD, in the present work we endeavored to summarize and discuss the pivotal literature findings regarding the eosinophilic COPD in order to help define the biological and clinical features of this peculiar phenotype, with particular attention to the use of established and emerging biomarkers, as well as current and future therapeutic perspectives.

The Role of Viral Infections in the Development and Progression of COPD

Chronic obstructive pulmonary disease (COPD) is a common chronic disease seen in smokers associated with poor functional status, quality of life, and morbidity and mortality from acute worsening of chronic symptoms, also called exacerbations. As a disease, the risk factors for COPD are well defined; however, there is room for innovation in identifying underlying biological processes, or "endotypes," that lead to the emergence and/or progression of COPD. Identifying endotypes allows for more thorough understanding of the disease, may reveal the means of disease prevention, and may be leveraged in novel therapeutic approaches. In this review, we discuss the interface of viral infections with both cellular and epithelial immunity as a potential endotype of interest in COPD.

[Assessment of blood eosinophil count in respiratory disease from primary care]

Most physicians in general, and family physicians in particular, are familiar with certain parameters when ordering a hematological study, such as hemoglobin (including hematocrit and its features), leukocytes (including lymphocytes) and platelets. Nevertheless, there are two values that we use to overlook which are eosinophils and basophils. Specifically, eosinophils have a tendency to increase with allergic pathology. This article focuses on this type of cells, helping to interpret the values obtained and highlighting their importance in two of the most frequent respiratory pathologies in primary care: asthma and COPD. In addition to observing how the increase or normality of these parameters condition the diagnosis, phenotype and even the treatment.

All-cause mortality and related factors in patients with varying degrees of peripheral blood eosinophilia

The aim of this study was to investigate all-cause mortality rates and related factors in patients with different levels of eosinophilia. This retrospective cohort study was conducted between January 2020 and December 2022 in the Internal Medicine Department of Dr Sadi Konuk Training and Research Hospital, Istanbul, Turkiye. A total of 161 patients with eosinophilia (at least 3 times) were included and divided into groups with absolute eosinophil counts of 500-999/µL (mild), 1000-1500/µL (moderate), and >1500/µL (severe). The mean age of patients was 65.67 ± 16.64 years at the time of admission, and 45 patients (57.8%) were male. The rates of mortality, oncological disease, and organ involvement were significantly higher in the severe group (P < .05). Increased serum total immunoglobulin E and vitamin B12, hematocrit value, eosinophil-to-lymphocyte ratio, and leukocyte were observed in eosinophilic patients. Decreased lymphocyte count, hemoglobin and hematocrit values were higher in deceased patients than in survivors (P < .05). Increased eosinophil-to-lymphocyte ratio, C-reactive protein, vitamin B12, and lactate dehydrogenase (LDH) activity were observed in participants who died compared to those who survived (P < .05). Multivariable logistic regression revealed that advanced age and higher LDH activity were independently associated with greater mortality risk while receiving non-steroid anti-inflammatory drugs or proton-pump inhibitors were associated with reduced mortality risk (P < .05). Advanced age and increased LDH activity were independently associated with greater risk for mortality, whereas absolute eosinophil counts was not. Considering the literature on this topic, our results show the need for further clinical and fundamental research to understand the role of eosinophils in human disease.

Association between Galectin-13 Expression and Eosinophilic Airway Inflammation in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) and asthma are chronic inflammatory diseases of the airways. Galectin-13 has recently been forwarded as a biomarker for airway eosinophilic inflammation in asthma. However, the association between galectin-13 and COPD remains unknown. To examine the changes in galectin-13 expression in acute exacerbations of COPD (AECOPD) and the stable phase of COPD and unveil the association between galectin-13 expression and eosinophilic inflammation in COPD, we measured plasma galectin-13 expression in different phases of COPD patients (n = 60, 44 AECOPD patients, and 16 stable COPD patients) and healthy controls (n = 15). Plasma levels of galectin-13 in 60 COPD patients were further analyzed and compared to systemic inflammation, airway eosinophilic inflammation, and lung function. The plasma galectin-13 level was markedly increased in subjects with AECOPD compared to stable COPD patients and healthy controls. Plasma galectin-13 levels in COPD subjects were positively correlated with serum CRP (r_s = 0.46, p = 0.0003), peripheral blood eosinophilia count (r_s = 0.57, p<0.0001), and FeNO (r_s = 0.46, p = 0.0002). In addition, the level of galectin-13 was negatively correlated with FEV₁ (r_s = -0.43, p = 0.0001), FEV₁ pred (%) (r_s = -0.544, p<0.0001), as well as FEV₁/FVC (r_s = -0.46, p<0.0001). Multiple linear regression analysis suggested that plasma galectin-13 levels were affected by FEV₁ pred (%), peripheral blood eosinophilia count, and FeNO. We concluded that galectin-13 levels were increased in COPD patients, and elevated galectin-13 expressions related to airway eosinophilic inflammation. Galectin-13 may facilitate the identification of COPD endotypes and may become a potential therapeutic target.

[Eosinophilic chronic obstructive pulmonary disease: A review]

Over the past decades, chronic obstructive pulmonary disease (COPD) has become a major public health problem due to increasing morbidity and mortality. COPD is characterized by airflow limitation due to inflammation of the bronchial tree and remodeling of the small airways. In 20-40% of patients with COPD, eosinophilic inflammation of the airways is observed, as in bronchial asthma. Eosinophilic COPD has recently been shown to be a distinct disease and is associated with more pronounced airway remodeling. Although the role of eosinophils in the pathogenesis of COPD is not fully understood, the level of eosinophils can be used in the prognosis and administration of corticosteroids, and their effectiveness is higher in eosinophilia. Currently, monoclonal antibodies directed against interleukins (IL-5, IL-4 and IL-13) or their receptors are being tested in the T2 endotype of COPD. This review focuses on the mechanisms of eosinophilia in COPD, the use of blood and sputum eosinophils as a biomarker, and the advisability of using monoclonal antibodies in the treatment of eosinophilic COPD.

Association of Upon-Diagnosis Blood Eosinophilic Count with Frequency and Severity of Annual Exacerbation in Chronic Obstructive Pulmonary Disease: A Prospective Longitudinal Analysis

Introduction

There is a controversy regarding the relationship between blood eosinophil count and COPD exacerbation. We aimed to determine whether peripheral eosinophils upon COPD diagnosis could affect the frequency and severity of annual acute exacerbation of COPD (AECOPD).

Methods

This prospective study was conducted on 973 newly diagnosed COPD patients who were under 1-year follow-up in a pulmonology center in Iran. The Cox proportional model, polynomial regression, and receiver operator characteristic curves were conducted to evaluate the impact of the eosinophil levels on AECOPD. A linear regression model was conducted to evaluate the continuous association of eosinophilic count with AECOPDs.

Results

Patients with eosinophil >200 cells/microliter were higher pack-year smokers with more pulmonary hypertension prevalence compared to COPD patients with <200 cells/microliter. There was a positive correlation between the eosinophilic count and the frequency of AECOPDs. Eosinophil >900 cells/microliter and eosinophil >600 cells/microliter had a sensitivity of 71.1% and 64.3%, respectively, in predicting the occurrence of more than one AECOPD. Eosinophilic count cutoff of 800 cells/microliter had the highest Youden index with sensitivity and specificity of 80.2% and 76.6%, respectively, for incident AECOPD in newly diagnosed patients. Using a linear model, increasing 180 cells/microliter in serum eosinophils was associated with further exacerbation. Evaluating gender, BMI, smoking pack-year, FEV1/FVC, CAT score, GOLD score, pulmonary hypertension, annual influenza, pneumococcal vaccinations, leukocytosis, and blood eosinophils, only blood eosinophils (hazard ratio (HR) = 1.44; 95% confidence interval = 1.33-2.15; p value = 0.03) and GOLD score (HR = 1.19; 95% CI = 1.30-1.52; p value = 0.03) were found as independent risk factors of AECOPD >3 episodes/year. Requirement for ICU admission, invasive ventilation, and mortality rate due to AECOPDs was similar between eosinophilic and noneosinophilic groups.

Conclusion

Eosinophilia upon COPD diagnosis is a factor of recurrent AECOPDs. To reduce the risk of AECOPDs and the burden of disease, clinicians may consider inhaler corticosteroids and domiciliary oxygen with a lower threshold for eosinophilic-COPD patients regardless of their clinical status.

[COPD and eosinophils]

COPD is a major cause of morbidity and mortality worldwide. As research progresses, new patient phenotypes are being defined, providing hope for more personalized management of the disease. A significant proportion of patients present with an increased level of blood eosinophils, which may reflect bronchial eosinophilic inflammation. The aims of this article are to characterize the role of eosinophils in COPD in terms of pathophysiology, associated respiratory symptoms, impact on treatment and, finally, to consider different future treatment options.