Sputum cell count: biomarkers in the differentiation of asthma, COPD and asthma-COPD overlap

Sputum microbiota and inflammatory subtypes in asthma, COPD, and its overlap

Background

Airway microbiota in asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) remains unknown.

Objective

This study with ACO-enriched population aimed to clarify airway microbiota in ACO and in mixed granulocytic inflammation, often detected in ACO and chronic airway diseases.

Methods

This is an observational cross-sectional study. Patients with asthma with airflow limitation, ACO, and COPD were enrolled. Blood tests, pulmonary function, exhaled nitric oxide, and sputum tests were conducted. Sputum microbiota was evaluated using the 16S rRNA gene sequencing technique.

Results

A total of 112 patients (13 asthma, 67 ACO, and 32 COPD) were examined. There were no significant differences in α-diversity among the 3 diseases. The relative abundances of phylum Bacteroidetes, class Bacteroidia, and genus Porphyromonas were associated with decreased eosinophilic inflammation, and were significantly lower in ACO than in COPD. In a comparison of sputum inflammatory subtypes, the proportion of Haemophilus was numerically highest in the mixed granulocytic subtype, followed by the neutrophilic subtype. Likewise, the proportion of Haemophilus was the highest in the intermediate-high (2%-8%) sputum eosinophil group and lowest in the severe (≥8%) eosinophil group. Clinically, Haemophilus proportion was associated with sputum symptoms. Finally, the proportion of Streptococcus was associated with higher blood eosinophil counts and most severe airflow limitation.

Conclusions

Bacteroidia and Porphyromonas abundances in sputum are associated with the eosinophil-low phenotype, and ACO may be characterized by a decrease in these taxa. A mild elevation in sputum eosinophil does not preclude the presence of Haemophilus, which should be noted in the management of obstructive airway diseases.

Airway inflammatory changes in the lungs of patients with asthma-COPD overlap (ACO): a bronchoscopy endobronchial biopsy study

BACKGROUND

Although asthma and chronic obstructive pulmonary disease (COPD) are two distinct chronic airway inflammatory diseases, they often co-exist in a patient and the condition is referred to as asthma-COPD overlap (ACO). Lack of evidence regarding the inflammatory cells in ACO airways has led to their poor prognosis and treatment. The objective of this endobronchial biopsy (EBB) study was to enumerate inflammatory cellular changes in the airway wall of ACO compared with asthma, COPD current smokers (CS) and ex-smokers (ES), normal lung function smokers (NLFS), and non-smoker controls (HC).

METHODS

EBB tissues from 74 patients were immunohistochemically stained for macrophages, mast cells, eosinophils, neutrophils, CD8+ T-cells and CD4+ T-cells. The microscopic images of stained tissues were evaluated in the epithelium, reticular basement membrane (RBM) cells/mm RBM length, and lamina propria (LP) cells/mm2 up to a depth of 120 µM using the image analysis software Image-Pro Plus 7.0. The observer was blinded to the images and disease diagnosis. Statistical analysis was performed using GraphPad Prism v9.

RESULTS

The tissue macrophages in ACO were substantially higher in the epithelium and RBM than in HC (P < 0.001 for both), COPD-ES (P < 0.001 for both), and -CS (P < 0.05 and < 0.0001, respectively). The ACO LP macrophages were significantly higher in number than COPD-CS (P < 0.05). The mast cell numbers in ACO were lower than in NLFS (P < 0.05) in the epithelium, lower than COPD (P < 0.05) and NLFS (P < 0.001) in RBM; and lower than  HC (P < 0.05) in LP. We noted lower eosinophils in ACO LP than HC (P < 0.05) and the lowest neutrophils in both ACO and asthma. Furthermore, CD8+ T-cell numbers increased in the ACO RBM than HC (P < 0.05), COPD-ES (P < 0.05), and NLFS (P < 0.01); however, they were similar in number in epithelium and LP across groups. CD4+ T-cells remained lower in number across all regions and groups.

CONCLUSION

These results suggest that the ACO airway tissue inflammatory cellular profile differed from the contributing diseases of asthma and COPD with a predominance of macrophages.

Increase in the level of oral neutrophils with gingival inflammation - A population survey

Objectives

Host responses to oral inflammation include a continuous and substantive response with the influx of polymorphonuclear leukocytes (PMN). PMN, referred to as first responders, migrate rapidly from the circulatory system through the connective tissue to mitigate stimuli and localize in the saliva. This study examined the relationship between the well-established clinical indices of gingivitis and dental plaque and the PMN level.

Materials and Methods

This study enrolled adults aged 18-75 years, who provided voluntary informed consent. Oral rinse samples were collected from 159 participants to estimate the PMN levels prior to the full-mouth assessment for gingivitis and dental plaque using the respective clinical indices.

Results

The gingival index and dental plaque index scores were in the range of 0.098-2.71 and 0.73-4.78, respectively. Regardless of the age and gender, higher number of PMN was observed with higher gingival index and dental plaque index scores. Our analyses indicated a significant correlation between the oral PMN level and gingival index with a correlation coefficient of 0.66 (p < 0.0001). Similarly, the correlation between the PMN level and dental plaque index was statistically significant with a correlation coefficient of 0.57 (p < 0.0001). Regression analysis identified a significant relationship between the PMN level and clinical indices (p < 0.0005).

Conclusions

Increase in the PMN levels with increasing clinical scores (gingival and dental plaque indices) reflect the oral inflammatory burden, irrespective of age or gender. These observations warrant future studies on participants stratified by health status and research directed toward examining the effects of interventions.

Clinical Indicators for Asthma-COPD Overlap: A Systematic Review and Meta-Analysis

Background

Some clinical indicators have been reported to be useful in differentiating asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) from pure asthma/COPD, but the results were inconsistent. This study aims to evaluate the diagnostic value of these indicators for ACO.

Methods

Databases of PubMed, EMBASE, Ovid and Web of Science were retrieved. Pooled standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated in random-effects models.

Results

48 eligible studies were included. The pooled results indicated, compared with pure asthma, ACO patients had lower levels of forced expiratory volume in the first second (FEV₁)% predicted (pred) (SMD=−1.09, 95% CI −1.3 to −0.87), diffusion lung capacity for carbon monoxide (DLCO)% pred (SMD=−0.83, 95% CI −1.24 to −0.42), fractional exhaled nitric oxide (FeNO) (SMD=−0.23, 95% CI −0.36 to −0.11), and higher levels of induced sputum neutrophil (SMD = 0.51, 95% CI 0.21 to 0.81), circulating YKL-40 (SMD = 0.96, 95% CI 0.27 to 1.64). However, relative to COPD alone, ACO patients had higher levels of FEV₁% pred (SMD = 0.15, 95% CI 0.05 to 0.26), DLCO% pred (SMD = 0.38, 95% CI 0.16 to 0.6), FeNO (SMD = 0.59, 95% CI 0.40 to 0.78), serum total immunoglobulin (Ig)E (SMD = 0.42, 95% CI 0.1 to 0.75), blood eosinophil (SMD = 0.44, 95% CI 0.29 to 0.59), induced sputum eosinophil (SMD = 0.62, 95% CI 0.42 to 0.83), and lower levels of induced sputum neutrophil (SMD=−0.48, 95% CI −0.7 to −0.27), circulating YKL-40 (SMD=−1.09, 95% CI −1.92 to −0.26).

Conclusion

Compared with pure asthma/COPD, ACO patients have different levels of FEV₁% pred, DLCO% pred, FeNO, serum total IgE, blood eosinophil, induced sputum eosinophil/neutrophil, and circulating YKL-40, which could be helpful to establish a clinical diagnosis of ACO.

Prevalence of asthma—chronic obstructive pulmonary disease overlap in patients with airflow limitation

Background

Asthma-COPD overlap (ACO) according to GINA and GOLD is not a single disease and is described by persistent airflow limitation with several features usually associated with asthma and several features usually associated with COPD. Some different protocols were proposed to diagnose ACO, besides those reported in GINA and GOLD guidelines. Despite the discrepancy between all the proposed diagnostic protocols, the diagnosis of ACO is still worthy as it may lead to a more appropriate treatment plan. In Egypt, prevalence of ACO is hardly estimated due to lack of database of patients. Our aim of work was to detect the prevalence of ACO in patients diagnosed as having a chronic airflow limiting disease.

Results

In asthma group (75 patients), 53.3% (40 patients) were diagnosed as ACO with 3 statistically significant favoring diagnostic criteria; post-BDR test FEV1/FVC < 70%, longer disease duration, and sputum neutrophilia ≥ 57%. While in COPD group (75 patients), 42.7% (32 patients) were diagnosed as ACO with four statistically significant favoring diagnostic criteria; higher BDR, presence of personal history of either asthma or atopy and sputum eosinophils > 1%.

Conclusions

ACO has an underestimated prevalence among those diagnosed with either asthma or COPD. More consensus guidelines are needed to focus on the more effective and the more practical criteria to diagnose such hidden disease.

Pathogenesis, clinical features of asthma COPD overlap (ACO), and therapeutic modalities

Both asthma and COPD are heterogeneous diseases identified by characteristic symptoms and functional abnormalities, with airway obstruction common in both diseases. Asthma COPD overlap (ACO) does not define a single disease but is a descriptive term for clinical use that includes several overlapping clinical phenotypes of chronic airways disease with different underlying mechanisms. This literature review was initiated to describe published studies, identify gaps in knowledge, and propose future research goals regarding the disease pathology of ACO, especially the airway remodelling changes and inflammation aspects. Airway remodelling occurs in asthma and COPD, but there are differences in the structures affected and the prime anatomic site at which they occur. Reticular basement membrane thickening and cellular infiltration with eosinophils and T-helper (CD4+) lymphocytes are prominent features of asthma. Epithelial squamous metaplasia, airway wall fibrosis, emphysema, bronchoalveolar lavage (BAL) neutrophilia and (CD8+) T-cytotoxic lymphocyte infiltrations in the airway wall are features of COPD. There is no universally accepted definition of ACO, nor are there clearly defined pathological characteristics to differentiate from asthma and COPD. Understanding etiological concepts within the purview of inflammation and airway remodelling changes in ACO would allow better management of these patients.

Current Knowledge of Asthma-COPD Overlap (ACO) Genetic Risk Factors, Characteristics, and Prognosis

Asthma-COPD overlap (ACO) is a newly identified phenotype of chronic obstructive airway diseases with shared asthma and COPD features. Patients with ACO are poorly defined, and some evidence suggests that they have worse health outcomes and greater disease burden than patients with COPD or asthma. Generally, there is no evidence-based and universal definition for ACO; several consensus documents have provided various descriptions of the phenotype. In addition, the mechanisms underlying the development of ACO are not fully understood. Whether ACO is a distinct clinical entity with its particular discrete genetic determinant different from asthma and COPD alone or an intermediate phenotype with overlapping genetic markers within asthma and COPD spectrum of obstructive airway disease remains unproven. This review summarizes the current knowledge of the genetic risk factors, characteristics, and prognosis of ACO.

ACO (Asthma-COPD Overlap) Is Independent from COPD: The Case in Favour

Over the last decade interest has been shown in people with symptomatic lung disease who have features both of COPD and asthma. In this review we examine how COPD and asthma are defined and examine clinical characteristics of people defined by researchers as having asthma-COPD overlap (ACO). We look at pathological and physiological features along with symptoms and consider the impact of each diagnosis upon therapeutic management. We highlight challenges in the diagnosis and management of airway disease and the various phenotypes that could be part of ACO, in so doing suggesting ways for the clinician to manage patients with features of both asthma and COPD.

Black Carbon Content in Airway Macrophages is Associated with Reduced CD80 Expression and Increased Exacerbations in Former Smokers With COPD

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by recurrent exacerbations. Macrophages play a critical role in immune response and tissue repair in COPD. Airway macrophages (AM) are exposed to environmental exposures which are retained in the cytoplasmic material. Both biomass and particulate matter have been linked to higher AM black carbon. It is unknown if AM black carbon is associated with COPD morbidity and macrophage phenotype.

METHODS

Former smokers with COPD were enrolled and sputum induction was performed to obtain airway macrophages. Macrophages underwent black carbon quantification and flow cytometry phenotyping. Health information was obtained the same day as sputum induction and prospective exacerbations were assessed by monthly telephone calls.

RESULTS

We studied 30 former smokers with COPD who had a mean age of 67 years and mean forced expiratory volume in 1 second (FEV1)% predicted of 60.8%. Higher AM black carbon content was associated with increased total exacerbations and severe exacerbations and reduced CD80 expression.

CONCLUSION

AM black carbon association with respiratory morbidity is largely unexplored and this is the first study to identify association with prospective exacerbations. Macrophages expressed reduced CD80, a surface marker providing costimulatory signals required for development of antigen-specific immune responses. Our findings suggest that reduced CD80 expression is the pathophysiologic mechanism for the association of AM black carbon content and increased exacerbations. Therefore, beyond solely serving as a marker for increased exposures, AM black carbon content may be a predictor of future exacerbations given a macrophage less equipped to respond to an acute infectious exposure.

Characteristics of Specialist-Diagnosed Asthma-COPD Overlap in Severe Asthma: Observations from the Korean Severe Asthma Registry (KoSAR)

BACKGROUND

While the clinical characteristics and outcomes of asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) have been frequently compared with those of COPD or asthma, the prevalence and features of ACO in patients with severe asthma are unclear.

OBJECTIVES

Evaluation of the prevalence and clinical features of ACO using the Korean severe asthma registry.

METHODS

At the time of registration, ACO was determined in patients with severe asthma by attending specialists. Patients were classified into ACO and non-ACO groups, and the demographic and clinical characteristics of these two groups were compared.

RESULTS

Of 482 patients with severe asthma, 23.7% had ACO. Patients in the ACO group were more likely to be male (P < .001), older (P < .001), and ex- or current smokers (P < .001) compared with those in the non-ACO group. Patients in the ACO group had lower mean forced expiratory volume in 1 second (P < .001) and blood eosinophil percentage (P = .006), but higher blood neutrophil percentage (P = .027) than those in the non-ACO group. The ACO group used more inhaled long-acting muscarinic antagonist (P < .001), methylxanthine (P = .001), or sustained systemic corticosteroid (P = .002). In addition, unscheduled emergency department visits due to exacerbation were more frequent in the ACO group (P = .006).

CONCLUSION

Among patients with severe asthma, those with ACO were older, predominantly male, and were more likely to have a smoking history than those with asthma only. Patients with ACO used more systemic corticosteroid and had more frequent exacerbations related to emergency department visits than those with severe asthma only.

Induced sputum metabolomic profiles and oxidative stress are associated with chronic obstructive pulmonary disease (COPD) severity: potential use for predictive, preventive, and personalized medicine

Chronic obstructive pulmonary disease (COPD) is a highly heterogeneous disease, and metabolomics plays a hub role in predictive, preventive, and personalized medicine (PPPM) related to COPD. This study thus aimed to reveal the role of induced sputum metabolomics in predicting COPD severity. In this pilot study, a total of 20 COPD patients were included. The induced sputum metabolites were assayed using a liquid chromatography-mass spectrometry (LC-MS/MS) system. Five oxidative stress products (myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione (GSH), neutrophil elastase (NE), and 8-iso-PGF2α) in induced sputum were measured by ELISA, and the metabolomic profiles were distinguished by principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA). The Kyoto Encyclopedia of Genes and Genomes (KEGG) was used for pathway enrichment analysis, and a significant difference in induced sputum metabolomics was observed between moderate and severe COPD. The KEGG analysis revealed that the glycerophospholipid metabolism pathway was downregulated in severe COPD. Due to the critical role of glycerophospholipid metabolism in oxidative stress, significant negative correlations were discovered between glycerophospholipid metabolites and three oxidative stress products (SOD, MPO, and 8-iso-PGF2α). The diagnostic values of SOD, MPO, and 8-iso-PGF2α in induced sputum were found to exhibit high sensitivities and specificities in the prediction of COPD severity. Collectively, this study provides the first identification of the association between induced sputum metabolomic profiles and COPD severity, indicating the potential value of metabolomics in PPPM for COPD management. The study also reveals the correlation between glycerophospholipid metabolites and oxidative stress products and their value for predicting COPD severity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-020-00227-w.

Asthma-Chronic Obstructive Pulmonary Disease Overlap

Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) defines a subgroup of patients with asthma who have persistent airflow obstruction or patients with COPD who may exhibit variable airflow limitation and/or evidence of type 2 inflammation. Additional investigations are needed to determine whether ACO represents a distinct disorder with unique underlying pathophysiology, whether ACO patients should be managed differently from those with asthma or COPD, and whether the diagnosis affects long-term outcomes. This article presents the data about the clinical features of ACO, the current information regarding the underlying pathophysiology of the syndrome, and current understanding of therapeutic options.

Eosinophils in COPD-Current Concepts and Clinical Implications

In recent years, heterogeneity in chronic obstructive pulmonary disease (COPD) inflammatory patterns has been recognized as a basis for more precise treatment interventions because current therapies have limited effectiveness. Eosinophilic airway inflammation in COPD has become a subject of research interest as a potential treatment target for inhaled corticosteroid therapy. However, the role of eosinophils in COPD is still unclear, and it is unknown why only some patients with COPD develop eosinophilic airway inflammation. Induced sputum analysis is the most common method of assessing the type of airway inflammation. Accessibility to sputum induction, however, is limited in clinical practice, and blood eosinophils have been proposed to serve as a surrogate marker and treatment guide. Blood eosinophil count has been shown to poorly predict sputum eosinophilia, and, moreover, it seems to be fairly unstable and affected by various factors. Nevertheless, in several trials, blood eosinophil count appeared to predict good response to inhaled corticosteroids However, biologics targeting eosinophils do not appear to be effective in COPD. In this review, we briefly summarize the current knowledge on eosinophils in COPD pathogenesis. Then, we discuss the use of blood eosinophil count in COPD in relation to the recent Global Initiative for Chronic Obstructive Pulmonary Disease recommendations, their ability to predict sputum eosinophilia, and their potential role in guiding treatment.

Biomarkers for chronic obstructive pulmonary disease diagnosis and progression: insights, disappointments and promise

PURPOSE OF REVIEW

This article reviews the status of biomarkers useful in the diagnosis and progression of chronic obstructive pulmonary disease (COPD). Biomarkers have been the focus of a great deal of COPD-related research in recent years, although useful markers in these specific arenas remain elusive.

RECENT FINDINGS

No biomarker other than lung function has been shown to be useful, to date, for the diagnosis of COPD. The best blood-based biomarkers for the progression of COPD may involve combinations of individual markers, such as CC16, fibrinogen and sRAGE. New imaging metrics, such as central airway collapse, pulmonary vascular changes and central airway branch variation, may be able to provide valuable prognostic and information, although these remain confined to research applications.

SUMMARY

Blood-based biomarkers for diagnosing and determining the progression of COPD remain disappointingly elusive. Although there have been some advances in nonblood-based markers, such as those from imaging, exhaled breath or physiologic assessment, these remain limited, for the most part, to research applications. Moving toward better markers that could be used in clinical application in the screening and diagnosis of COPD that could also provide prognostic information remains an important goal of research.

The many faces of asthma-chronic obstructive pulmonary disease overlap

PURPOSE OF REVIEW

Asthma and chronic obstructive pulmonary disease (COPD) are common diseases that often overlap. The term asthma-COPD overlap (ACO) has been used to define this entity but there remain several speculations on its exact definition, impact, pathophysiology, clinical features, and management. We reviewed recent publications on ACO to obtain more insight of current knowledge and outline future needs.

RECENT FINDINGS

Criteria for ACO vary from one publication to another and the many variable features of these patients underline the need to reconsider the evaluation and approach of patients with overlapping features based on clinical traits and underlying biological mechanisms. Epidemiological studies reveal that ACO patients have generally an increased burden of illness and healthcare use in addition to poorer quality of life (QoL) compared with asthma and higher or equal to COPD. However, their long-term outcome seems better than patients with COPD alone. Various methods have been proposed to evaluate these patients but their usefulness compared to 'classical' investigation of obstructive lung diseases remains speculative and needs further evaluation. Furthermore, there are no formal studies that examined and compared the different treatment strategies of well-characterized patients with ACO as such patients are usually excluded from clinical trials.

SUMMARY

ACO is a common condition with variable features and a high burden of disease. There is no consensus on its definition, diagnostic, and clinical features and more research should be done on its optimal management and long-term outcomes.

[Correlation between expressions of myeloperoxidase and eosinophil cationic protein in sputum and clinical features of asthma-chronic obstructive pulmonary disease overlap]

OBJECTIVE

To observe the role of myeloperoxidase(MPO)and eosinophilic cationic protein(ECP)in the airway inflammation and their correlation with clinical feature in asthma-COPD overlap (ACO) patients.

METHODS

Twenty patients with COPD, 20 with asthma, 20 with ACO and 20 control subjects underwent pulmonary function test for measurement of forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), peak expiratory flow (PEF), and maximum midexpiratory flow (MMF_25/75). COPD assessment test (CAT) was used to evaluate the clinical symptoms of the patients with COPD and ACO. The asthma control test (ACT) was used to evaluate the asthma control in the patients with asthma and ACO. Induced sputum samples were collected from the subjects for analysis of neutrophil and eosinophil ratios, and enzyme-linked immunosorbent assay was used to determine the expression levels of MPO and ECP in the sputum.

RESULTS

No significant difference was observed in the CAT scores between ACO group and COPD group (P&gt; 0.05). Compared with the asthma group, the patients with ACO had significantly lower ACT scores and lower FEV₁, PEF and MMF_25/75 (P &lt; 0.05). The patients with ACO had significantly higher FVC and sputum eosinophil ratio than those with COPD (P &lt; 0.05), and a higher sputum neutrophil ratio than those with asthma (P &lt; 0.01). In ACO group, the MPO level in sputum was significantly higher than that in the asthma group (P &lt; 0.05), while sputum ECP level was significantly higher than that in both the asthma group and COPD group (P &lt; 0.05 or 0.01). In ACO group, sputum MPO level was positively correlated with sputum neutrophil ratio (r=0.8358, P &lt; 0.01) but was not correlated with CAT score or FEV₁ (P&gt; 0.05); sputum ECP level was positively correlated with sputum eosinophil ratio (r=0.4666, P &lt; 0.05) and was inversely correlated with ACT score (r=-0.4966, P &lt; 0.05) and FEV₁ (r=-0.4610, P &lt; 0.05).

CONCLUSIONS

Both neutrophilic and eosinophilic inflammations occur in the airway of patients with ACO, and their sputum ECP level is negatively correlated with asthma control and obstructive airflow limitation.

Predictors of Asthma/COPD Overlap in FDNY Firefighters With World Trade Center Dust Exposure: A Longitudinal Study

BACKGROUND

Previously healthy firefighters with World Trade Center (WTC) dust exposure developed airway disease. Risk factors for irritant-associated asthma/COPD overlap are poorly defined.

METHODS

This study included 2,137 WTC-exposed firefighters who underwent a clinically indicated bronchodilator pulmonary function test (BD-PFT) between 9/11/2001 and 9/10/2017. A post-BD FEV₁ increase of > 12% and 200 mL from baseline defined asthma, and a post-BD FEV₁/FVC ratio < 0.7 identified COPD cases. Participants who met both criteria had asthma/COPD overlap. Eosinophil levels were measured on screening blood tests performed shortly after 9/11/2001 and prior to BD-PFT; a subgroup of participants also had serum IgE and 21 cytokines measured (n = 215). Marginal Cox regression models for multiple events assessed the associations of eosinophil levels or serum biomarkers with subsequent diagnosis, with age, race, smoking, WTC exposure, first post-9/11 FEV₁/FVC ratio, and BMI included as covariates.

RESULTS

BD-PFT diagnosed asthma/COPD overlap in 99 subjects (4.6%), isolated-asthma in 202 (9.5%), and isolated-COPD in 215 (10.1%). Eosinophil concentration ≥ 300 cells/μL was associated with increased risk of asthma/COPD overlap (hazard ratio [HR], 1.85; 95% CI, 1.16-2.95) but not with isolated-asthma or isolated-COPD. Serum IL-4 also predicted asthma/COPD overlap (HR, 1.51 per doubling of cytokine concentration; 95% CI, 1.17-1.95). Greater IL-21 concentration was associated with both isolated-asthma and isolated-COPD (HRs of 1.73 [95% CI, 1.27-2.35] and 2.06 [95% CI, 1.31-3.23], respectively).

CONCLUSIONS

In WTC-exposed firefighters, elevated blood eosinophil and IL-4 levels are associated with subsequent asthma/COPD overlap. Disease-specific T-helper cell type 2 biomarkers present years before diagnosis suggest patient-intrinsic predisposition to irritant-associated asthma/COPD overlap.