Pulmonary biomarkers in COPD exacerbations: a systematic review

Biological and technical factors affecting the point-of-care diagnostics in not-oncological chronic diseases

Inexpensive point-of-care (POC) analytical solutions have the potential to allow the implementation of large-scale screening campaigns aimed at identifying the initial stages of pathologies in the population, reducing morbidity, mortality and, indirectly, also the costs for the healthcare system. At global level, the most common preventive screening schemes address some cancer pathologies or are used to monitor the spread of some infective diseases. However, systematic testing might become decisive to improve the care response even in the case of chronic pathologies and, in this review, we analyzed the state-of-the-art of the POC diagnostics for Chronic Kidney Disease, Chronic Obstructive Pulmonary Disease and Multiple Sclerosis. The different technological options used to manufacture the biosensors and evaluate the produced data have been described and this information has been integrated with the present knowledge relatively to the biomarkers that have been proposed to monitor such diseases, namely their availability and reliability. Finally, the nature of the macromolecules used to capture the biomarkers has been discussed in relation to the biomarker nature.

Deterioration Patterns in Patients Admitted for Severe COPD Exacerbation

BACKGROUND

Chronic obstructive pulmonary disease (COPD) exacerbations represent significant clinical events marked by worsening respiratory symptoms, often necessitating changes in medication or hospitalization. Identifying patterns of exacerbation and understanding their clinical implications are critical for improving patient outcomes. This study aimed to identify exacerbation patterns in COPD patients using variations in the COPD Assessment Test (CAT) scores and compare clinical characteristics and comorbidities among patients with different exacerbation patterns.

METHODS

An observational study was conducted involving COPD patients admitted for severe exacerbations. The administered CAT questionnaire referred to two periods: (1) the period during hospital admission and (2) the stable period two months prior to admission.

RESULTS

Fifty patients (60% male, mean age 70.5 years, standard deviation [SD] 9.6) were included; of these, eight (16%) were active smokers. Significant worsening in CAT scores during the exacerbation compared to the stable period was observed (25 vs. 13.5, p < 0.001). Three exacerbation patterns were identified: increased cough and sputum (cluster 1); increased dyspnea and activity limitation (cluster 2); and poorer sleep quality and lower energy (cluster 3). No significant differences were found regarding demographics and lung function.

CONCLUSIONS

Three distinct exacerbation patterns were identified in COPD patients based on CAT score variations, suggesting that exacerbations are heterogeneous events. Future studies with larger sample sizes and prospective follow-up are necessary to validate these findings and explore their clinical and prognostic implications.

Remote Patient Monitoring and Machine Learning in Acute Exacerbations of Chronic Obstructive Pulmonary Disease: Dual Systematic Literature Review and Narrative Synthesis

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are associated with high mortality, morbidity, and poor quality of life and constitute a substantial burden to patients and health care systems. New approaches to prevent or reduce the severity of AECOPD are urgently needed. Internationally, this has prompted increased interest in the potential of remote patient monitoring (RPM) and digital medicine. RPM refers to the direct transmission of patient-reported outcomes, physiological, and functional data, including heart rate, weight, blood pressure, oxygen saturation, physical activity, and lung function (spirometry), directly to health care professionals through automation, web-based data entry, or phone-based data entry. Machine learning has the potential to enhance RPM in chronic obstructive pulmonary disease by increasing the accuracy and precision of AECOPD prediction systems.

OBJECTIVE

This study aimed to conduct a dual systematic review. The first review focuses on randomized controlled trials where RPM was used as an intervention to treat or improve AECOPD. The second review examines studies that combined machine learning with RPM to predict AECOPD. We review the evidence and concepts behind RPM and machine learning and discuss the strengths, limitations, and clinical use of available systems. We have generated a list of recommendations needed to deliver patient and health care system benefits.

METHODS

A comprehensive search strategy, encompassing the Scopus and Web of Science databases, was used to identify relevant studies. A total of 2 independent reviewers (HMGG and CM) conducted study selection, data extraction, and quality assessment, with discrepancies resolved through consensus. Data synthesis involved evidence assessment using a Critical Appraisal Skills Programme checklist and a narrative synthesis. Reporting followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.

RESULTS

These narrative syntheses suggest that 57% (16/28) of the randomized controlled trials for RPM interventions fail to achieve the required level of evidence for better outcomes in AECOPD. However, the integration of machine learning into RPM demonstrates promise for increasing the predictive accuracy of AECOPD and, therefore, early intervention.

CONCLUSIONS

This review suggests a transition toward the integration of machine learning into RPM for predicting AECOPD. We discuss particular RPM indices that have the potential to improve AECOPD prediction and highlight research gaps concerning patient factors and the maintained adoption of RPM. Furthermore, we emphasize the importance of a more comprehensive examination of patient and health care burdens associated with RPM, along with the development of practical solutions.

Increased serum IL‑41 associated with acute exacerbation of chronic obstructive pulmonary disease

Interleukin (IL)-41 is a novel immunomodulatory cytokine involved in the pathogenesis of several inflammatory and metabolic illnesses. However, it remains unclear how IL-41 contributes to the pathogenesis of chronic obstructive pulmonary disease (COPD). Therefore, the aim of the present study was to explore the correlation between the expression level of IL-41 and acute exacerbation of COPD (AECOPD). In total, 107 patients with COPD and 56 healthy controls were recruited from the First Affiliated Hospital of Ningbo University (Ningbo, China). Serum IL-41, IL-6, and matrix metalloproteinase-2 (MMP-2) levels were evaluated using enzyme-linked immunosorbent assay. Serum amyloid A (SAA) and C-reactive protein (CRP) levels were assessed in the hospital laboratory. The levels of IL-41 were higher in the AECOPD group than in the stable COPD (SCOPD) and control groups (P<0.0001). IL-6, SAA and CRP levels, the percentage of neutrophils, as well as neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios were higher in the AECOPD group than those in the SCOPD and control groups. The smoking index was positively correlated with serum IL-41, CRP and SAA levels. The expression level of IL-41 was correlated with the number of acute exacerbations, severity of the exacerbations, and COPD assessment test scores in the AECOPD group. Examination of the receiver operating characteristic (ROC) curves showed that IL-41, especially when combined with other inflammatory factors, had a specific diagnostic value for AECOPD. According to the ROC curve analysis, the area under the curve (AUC) for IL-41 was 0.742 (P=0.051), and the AUC for IL-41 combined with other inflammatory factors was 0.925 (P=0.030). Increased serum IL-41 levels were associated with AECOPD and may play a role in the monitoring and evaluation of COPD.

Early diagnostic BioMARKers in exacerbations of chronic obstructive pulmonary disease: protocol of the exploratory, prospective, longitudinal, single-centre, observational MARKED study

INTRODUCTION

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) play a pivotal role in the burden and progressive course of chronic obstructive pulmonary disease (COPD). As such, disease management is predominantly based on the prevention of these episodes of acute worsening of respiratory symptoms. However, to date, personalised prediction and early and accurate diagnosis of AECOPD remain unsuccessful. Therefore, the current study was designed to explore which frequently measured biomarkers can predict an AECOPD and/or respiratory infection in patients with COPD. Moreover, the study aims to increase our understanding of the heterogeneity of AECOPD as well as the role of microbial composition and hostmicrobiome interactions to elucidate new disease biology in COPD.

METHODS AND ANALYSIS

The 'Early diagnostic BioMARKers in Exacerbations of COPD' study is an exploratory, prospective, longitudinal, single-centre, observational study with 8-week follow-up enrolling up to 150 patients with COPD admitted to inpatient pulmonary rehabilitation at Ciro (Horn, the Netherlands). Respiratory symptoms, vitals, spirometry and nasopharyngeal, venous blood, spontaneous sputum and stool samples will be frequently collected for exploratory biomarker analysis, longitudinal characterisation of AECOPD (ie, clinical, functional and microbial) and to identify host-microbiome interactions. Genomic sequencing will be performed to identify mutations associated with increased risk of AECOPD and microbial infections. Predictors of time-to-first AECOPD will be modelled using Cox proportional hazards' regression. Multiomic analyses will provide a novel integration tool to generate predictive models and testable hypotheses about disease causation and predictors of disease progression.

ETHICS AND DISSEMINATION

This protocol was approved by the Medical Research Ethics Committees United (MEC-U), Nieuwegein, the Netherlands (NL71364.100.19).

TRIAL REGISTRATION NUMBER

NCT05315674.

EVs-miRNA: The New Molecular Markers for Chronic Respiratory Diseases

Idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma and sleep disorders are chronic respiratory diseases that affect the airways, compromising lung function over time. These diseases affect hundreds of millions of people around the world and their frequency seems to be increasing every year. Extracellular vesicles (EVs) are small-sized vesicles released by every cell in the body. They are present in most body fluids and contain various biomolecules including proteins, lipids, mRNA and non-coding RNA (micro-RNA). The EVs can release their cargo, specifically micro-RNAs (miRNAs), to both neighboring and/or distal cells, playing a fundamental role in cell-cell communication. Recent studies have shown their possible role in the pathogenesis of various chronic respiratory diseases. The expression of miRNAs and, in particular, of miRNAs contained within the extracellular vesicles seems to be a good starting point in order to identify new potential biomarkers of disease, allowing a non-invasive clinical diagnosis. In this review we summarize some studies, present in the literature, about the functions of extracellular vesicles and miRNAs contained in extracellular vesicles in chronic respiratory diseases and we discuss the potential clinical applications of EVs and EVs-miRNAs for their possible use such as future biomarkers.

Telemedicine and virtual respiratory care in the era of COVID-19

The World Health Organization defines telemedicine as “an interaction between a health care provider and a patient when the two are separated by distance”. The COVID-19 pandemic has forced a dramatic shift to telephone and video consulting for follow up and routine ambulatory care for reasons of infection control. Short Message Service (“text”) messaging has proved a useful adjunct to remote consulting allowing transfer of photographs and documents. Maintaining non-communicable diseases care is a core component of pandemic preparedness and telemedicine has developed to enable (for example) remote monitoring of sleep apnoea, telemonitoring of chronic obstructive pulmonary disease, digital support for asthma self-management, remote delivery of pulmonary rehabilitation. There are multiple exemplars of telehealth instigated rapidly to provide care for people with COVID-19, to manage the spread of the pandemic, or to maintain safe routine diagnostic or treatment services.

Despite many positive examples of equivalent functionality and safety, there remain questions about the impact of remote delivery of care on rapport and the longer-term impact on patient/professional relationships. Although telehealth has the potential to contribute to universal health coverage by providing cost-effective accessible care, there is a risk of increasing social health inequalities if the “digital divide” excludes those most in need of care. As we emerge from the pandemic, the balance of remote versus face-to-face consulting, and the specific role of digital health in different clinical and healthcare contexts will evolve. What is clear is that telemedicine in one form or another will be part of the “new norm”.

Incorporating Biomarkers in COPD Management: The Research Keeps Going

Globally, chronic obstructive pulmonary disease (COPD) remains a major cause of morbidity and mortality, having a significant socioeconomic effect. Several molecular mechanisms have been related to COPD including chronic inflammation, telomere shortening, and epigenetic modifications. Nowadays, there is an increasing need for novel therapeutic approaches for the management of COPD. These treatment strategies should be based on finding the source of acute exacerbation of COPD episodes and estimating the patient’s own risk. The use of biomarkers and the measurement of their levels in conjunction with COPD exacerbation risk and disease prognosis is considered an encouraging approach. Many types of COPD biomarkers have been identified which include blood protein biomarkers, cellular biomarkers, and protease enzymes. They have been isolated from different sources including peripheral blood, sputum, bronchoalveolar fluid, exhaled air, and genetic material. However, there is still not an exclusive biomarker that is used for the evaluation of COPD but rather a combination of them, and this is attributed to disease complexity. In this review, we summarize the clinical significance of COPD-related biomarkers, their association with disease outcomes, and COPD patients’ management. Finally, we depict the various samples that are used for identifying and measuring these biomarkers.

A Novel Processing-Free Method for RNAseq Analysis of Spontaneous Sputum in Chronic Obstructive Pulmonary Disease

Background: Assessments of airways inflammation in patients with chronic obstructive pulmonary disease (COPD) require semi-invasive procedures and specialized sample processing know-how. In this study we aimed to set up and validate a novel non-invasive processing-free method for RNA sequencing (RNAseq) of spontaneous sputum samples collected from COPD patients.

Methods: Spontaneous sputum samples were collected and stabilized, with or without selection of plugs and with or without the use of a stabilizer specifically formulated for downstream diagnostic testing (PrimeStore® Molecular Transport Medium). After 8 days storage at ambient temperature RNA was isolated according to an optimized RNAzol® method. An average percentage of fragments longer than 200 nucleotides (DV₂₀₀) >30% and an individual yield >50 ng were required for progression of samples to sequencing. Finally, to assess if the transcriptome generated would reflect a true endotype of COPD inflammation, the outcome of single-sample gene-set enrichment analysis (ssGSEA) was validated using an independent set of processed induced sputum samples. Results: RNA extracted from spontaneous sputum using a stabilizer showed an average DV₂₀₀ higher than 30%. 70% of the samples had a yield >50 ng and were submitted to downstream analysis. There was a straightforward correlation in terms of gene expression between samples handled with or without separation of plugs. This was also confirmed by principal component analysis and ssGSEA. The top ten enriched pathways resulting from spontaneous sputum ssGSEA were associated to features of COPD, namely, inflammation, immune responses and oxidative stress; up to 70% of these were in common within the top ten enriched pathways resulting from induced sputum ssGSEA.

Conclusion: This analysis confirmed that the typical COPD endotype was represented within spontaneous sputum and supported the current method as a non-invasive processing-free procedure to assess the level of sputum cell inflammation in COPD patients by RNAseq analysis.

Chronic Obstructive Pulmonary Disease: Epidemiology, Biomarkers, and Paving the Way to Lung Cancer

Chronic obstructive pulmonary disease (COPD), the frequently fatal pathology of the respiratory tract, accounts for half a billion cases globally. COPD manifests via chronic inflammatory response to irritants, frequently to tobacco smoke. The progression of COPD from early onset to advanced disease leads to the loss of the alveolar wall, pulmonary hypertension, and fibrosis of the respiratory epithelium. Here, we focus on the epidemiology, progression, and biomarkers of COPD with a particular connection to lung cancer. Dissecting the cellular and molecular players in the progression of the disease, we aim to shed light on the role of smoking, which is responsible for the disease, or at least for the more severe symptoms and worse patient outcomes. We summarize the inflammatory conditions, as well as the role of EMT and fibroblasts in establishing a cancer-prone microenvironment, i.e., the soil for ‘COPD-derived’ lung cancer. We highlight that the major health problem of COPD can be alleviated via smoking cessation, early diagnosis, and abandonment of the usage of biomass fuels on a global basis.

Detection of respiratory viruses and expression of inflammatory cytokines in patients with acute exacerbation chronic obstructive pulmonary disease in Mongolia China

Chronic obstructive pulmonary disease (COPD) was estimated to be the third cause of global mortality by 2020. Acute exacerbation COPD (AECOPD) is a sudden worsening of COPD symptoms and could be due to virus/bacterial infections and air pollution. Increased expression of inflammatory markers in patients with AECOPD is associated with viral infection. This study aimed to detect different viruses and analyze the expression of various inflammatory markers associated with AECOPD patients. Three hundred and forty-seven patients diagnosed with COPD according to GOLD criteria were included in this study. Swab samples and blood were collected for the detection of viruses by RT-PCR and expression of inflammatory markers, respectively. Of the swab samples, 113 (32.6%) of samples were positive for virus detection. Of these, HRV (39.8%) was the predominant virus detected followed by FluB (27.4%) and FluA (22.1%). The presence of HRV was significantly higher (p=0.044) among the other detected viruses. When compared to healthy controls the expression levels of TNF-α, IL-6 and IL-8 were significantly higher (p<0.05) in virus-positive patients. The IL-6 and IL-8 were the next predominantly expressed in markers among the samples. The higher expression rate of IL-8 was significantly (p<0.05) associated with patients having COPD GOLD III severity level and smoking history. Although HRV was the predominant virus detected the combined prevalence of Influenza A and B surpassing the rate of HRV. The high-level expression of well known inflammatory markers of AECOPD, TNF-α, IL-6 and IL-8 indicates a chronic severe illness. These markers play an important role and could be used as a marker for determining the severity of AECOPD.

Uncovering the Role of Oxidative Imbalance in the Development and Progression of Bronchial Asthma

Asthma is a chronic inflammatory disease of the airways related to epithelial damage, bronchial hyperresponsiveness to contractile agents, tissue remodeling, and luminal narrowing. Currently, there are many data about the pathophysiology of asthma; however, a new aspect has emerged related to the influence of reactive oxygen and nitrogen species (ROS and RNS) on the origin of this disease. Several studies have shown that an imbalance between the production of ROS and RNS and the antioxidant enzymatic and nonenzymatic systems plays an important role in the pathogenesis of this disease. Considering this aspect, this study is aimed at gathering data from the scientific literature on the role of oxidative distress in the development of inflammatory airway and lung diseases, especially bronchial asthma. For that, articles related to these themes were selected from scientific databases, including human and animal studies. The main findings of this work showed that the respiratory system works as a highly propitious place for the formation of ROS and RNS, especially superoxide anion, hydrogen peroxide, and peroxynitrite, and the epithelial damage is reflected in an important loss of antioxidant defenses that, in turn, culminates in an imbalance and formation of inflammatory and contractile mediators, such as isoprostanes, changes in the activity of protein kinases, and activation of cell proliferation signalling pathways, such as the MAP kinase pathway. Thus, the oxidative imbalance appears as a promising path for future investigations as a therapeutic target for the treatment of asthmatic patients, especially those resistant to currently available therapies.

Small Airways Disease, Biomarkers and COPD: Where are We?

The response to treatment and progression of Chronic Obstructive Pulmonary Disease (COPD) varies significantly. Small airways disease (SAD) is being increasingly recognized as a key pathological feature of COPD. Studies have brought forward pathological evidence of small airway damage preceding the development of emphysema and the detection of obstruction using traditional spirometry. In recent years, there has been a renewed interest in the early detection of SAD and this has brought along an increased demand for physiological tests able to identify and quantify SAD. Early detection of SAD allows early targeted therapy and this suggests the potential for altering the course of disease. The aim of this article is to review the evidence available on the physiological testing of small airways. The first half will focus on the role of lung function tests such as maximum mid-expiratory flow, impulse oscillometry and lung clearance index in detecting and quantifying SAD. The role of Computed Tomography (CT) as a radiological biomarker will be discussed as well as the potential of recent CT analysis software to differentiate normal aging of the lungs to pathology. The evidence behind SAD biomarkers sourced from blood as well as biomarkers sourced from sputum and broncho-alveolar lavage (BAL) will be reviewed. This paper focuses on CC-16, sRAGE, PAI-1, MMP-9 and MMP-12.

Intra-alveolar neutrophil-derived microvesicles are associated with disease severity in COPD

Despite advances in the pathophysiology of chronic obstructive pulmonary disease (COPD), there is a distinct lack of biochemical markers to aid clinical management. Microvesicles (MVs) have been implicated in the pathophysiology of inflammatory diseases including COPD, but their association to COPD disease severity remains unknown. We analyzed different MV populations in plasma and bronchoalveolar lavage fluid (BALF) taken from 62 patients with mild to very severe COPD (51% male; mean age: 65.9 yr). These patients underwent comprehensive clinical evaluation (symptom scores, lung function, and exercise testing), and the capacity of MVs to be clinical markers of disease severity was assessed. We successfully identified various MV subtype populations within BALF [leukocyte, polymorphonuclear leukocyte (PMN; i.e., neutrophil), monocyte, epithelial, and platelet MVs] and plasma (leukocyte, PMN, monocyte, and endothelial MVs) and compared each MV population to disease severity. BALF neutrophil MVs were the only population to significantly correlate with the clinical evaluation scores including forced expiratory volume in 1 s, modified Medical Research Council dyspnea score, 6-min walk test, hyperinflation, and gas transfer. BALF neutrophil MVs, but not neutrophil cell numbers, also strongly correlated with BODE index. We have undertaken, for the first time, a comprehensive evaluation of MV profiles within BALF/plasma of COPD patients. We demonstrate that BALF levels of neutrophil-derived MVs are unique in correlating with a number of key functional and clinically relevant disease severity indexes. Our results show the potential of BALF neutrophil MVs for a COPD biomarker that tightly links a key pathophysiological mechanism of COPD (intra-alveolar neutrophil activation) with clinical severity/outcome.

A Sputum 6 Gene Expression Signature Predicts Inflammatory Phenotypes and Future Exacerbations of COPD

Background

The 6 gene expression signature (6GS) predicts inflammatory phenotype, exacerbation risk, and corticosteroid responsiveness in asthma. In COPD, patterns of airway inflammation are similar, suggesting the 6GS may be useful. This study determines the diagnostic and prognostic ability of 6GS in predicting inflammatory phenotypes and exacerbation risk in COPD.

Methods

We performed 2 studies: a cross-sectional phenotype prediction study in stable COPD (total N=132; n=34 eosinophilic (E)-COPD, n=42 neutrophilic (N)-COPD, n=39 paucigranulocytic (PG)-COPD, n=17 mixed-granulocytic (MG)-COPD) that assessed 6GS ability to discriminate phenotypes (eosinophilia≥3%; neutrophilia≥61%); and a prospective cohort study (total n=54, n=8 E-COPD; n=18 N-COPD; n=20 PG-COPD; n=8 MG-COPD, n=21 exacerbation prone (≥2/year)) that investigated phenotype and exacerbation prediction utility. 6GS was measured by qPCR and evaluated using multiple logistic regression and area under the curve (AUC). Short-term reproducibility (intra-class correlation) and phenotyping method agreement (κ statistic) were assessed.

Results

In the phenotype prediction study, 6GS could accurately identify and discriminate patients with E-COPD from N-COPD (AUC=96.4%; p<0.0001), PG-COPD (AUC=88.2%; p<0.0001) or MG-COPD (AUC=86.2%; p=0.0001), as well as N-COPD from PG-COPD (AUC=83.6%; p<0.0001) or MG-COPD (AUC=87.4%; p<0.0001) and was reproducible. In the prospective cohort study, 6GS had substantial agreement for neutrophilic inflammation (82%, κ=0.63, p<0.001) and moderate agreement for eosinophilic inflammation (78%, κ=0.42, p<0.001). 6GS could significantly discriminate exacerbation prone patients (AUC=77.2%; p=0.034). Higher IL1B levels were associated with poorer lung function and increased COPD severity.

Conclusion

6GS can significantly and reproducibly discriminate COPD inflammatory phenotypes and predict exacerbation prone patients and may become a useful molecular diagnostic tool assisting COPD management.

GTS-21, an α7nAChR agonist, suppressed the production of key inflammatory mediators by PBMCs that are elevated in COPD patients and associated with impaired lung function

Chronic obstructive pulmonary disease (COPD) is a lung inflammatory disease characterized by progressive airflow limitation, chronic respiratory symptoms and frequent exacerbations. There is an unmet need to identify novel therapeutic alternatives beside bronchodilators that prevent disease progression. Levels of both Nitric Oxide (NO) and IL-6 were significantly increased in the plasma of patients in the exacerbation phase (ECOPD, n = 13) when compared to patients in the stable phase (SCOPD, n = 38). Levels of both NO and IL-6 were also found to inversely correlate with impaired lung function (%FEV1 predicted). In addition, there was a strong positive correlation between levels of IL-6 and NO found in the plasma of patients and those spontaneously produced by their peripheral blood mononuclear cells (PBMCs), identifying these cells as a major source of these key inflammatory mediators in COPD. GTS-21, an agonist for the alpha 7 nicotinic receptors (α7nAChR), was found to exert immune-modulatory actions in PBMCs of COPD patients by suppressing the production of IL-6 and NO. This study provides the first evidence supporting the therapeutic potential of α7nAChR agonists in COPD due to their ability to suppress the production of key inflammatory markers associated with disease severity.

Electrochemical methods for detection of biomarkers of Chronic Obstructive Pulmonary Disease in serum and saliva

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death nowadays, and its underdiagnosis is still a great challenge. More effective diagnosis method is in urgent need since the traditional spirometry has many limitations in the practical application. The electrochemical (EC) detection methods have their unique advantages of high accuracy, short response time and easy integration of the system. In this review, recent works on the EC methods for COPD biomarkers including interleukin 6 (IL-6), interleukin 8 (IL-8) and C-reactive protein (CRP) are summarized. Five types of EC methods are highlighted in this study, as enzyme-labelled immunosensors, nanoparticle-labelled immunosensors, capacitive or impedimetric immunosensors, magnetoimmunosensors, and field effect transistor (FET) immunosensors. To date, EC immunosensors have been exhibiting high analytical performance with a detection limit that can achieve several pg/mL or even lower. The simplicity of EC immunosensors makes them a perfect solution for a future point-of-care device to use in settings for COPD diagnosis and follow-up. Nevertheless, more efforts need to be paid on the simultaneous detection of multiple biomarkers, a demand for the clinical diagnosis, and processes of assay simplification towards achieving one-step detection.

The acute wheezy adult with airways disease in the emergency department: a retrospective case-note review of exacerbations of COPD

Introduction: There has been an increase in interest in the peripheral blood eosinophil count as a biomarker in COPD. Few studies have examined the eosinophil count in patients attending the emergency department (ED) with acute exacerbations of COPD (AECOPD). We investigated the relationship between the blood eosinophil and other variables collected routinely at ED presentation and outcomes. Methods: Retrospective case note review of patients attending the ED with an AECOPD over 18 months. Demographic, clinical and pharmacological data were analyzed at the time of presentation, and clinical outcomes relating to hospital admission, length of hospital stay and mortality were investigated. Results: There were 743 AECOPD index events in 537 patients. Over half (57%) of all attendees were admitted to hospital. They were older, reported an increased number of exacerbations and higher levels of total leukocytes and neutrophils. Length of stay was shorter in patients with a blood eosinophil count ≥2% compared to <2% (median (IQR) 3 days (1-7) vs 4 days (2-8) respectively, p<0.05). Length of stay correlated with peripheral blood neutrophils (r=0.12, p=0.021), peripheral blood absolute and relative eosinophils (r=-0.12, p=0.024 and r=-0.11, p=0.035, respectively) and CRP (r=0.16, p=0.027). Non-eosinophilic AECOPD were associated with an increased risk of mortality during an exacerbation (χ2 5.9, OR 3.08, 95% CI 1.19-7.96, p=0.015). Conclusion: In exacerbations of COPD presenting to ED, a higher blood eosinophil count is associated with a shorter length of stay and reduced mortality.

Monitoring Antioxidant Enzyme Activity during Exacerbations of Chronic Obstructive Pulmonary Disease

Superoxide dismutases (SODs) and catalase (CAT) have been implicated as major antioxidant enzymes of the human lungs. In this study, we investigated whether activities of these enzymes are altered in the airways of patients hospitalized with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). SOD and CAT activities were measured in the sputum, exhaled breath condensate, and serum of 36 COPD patients experiencing a severe exacerbation. Measurements were performed using colorimetric assays in samples collected at the time of hospital admission and at the time of hospital discharge following treatment of AECOPD. For comparison, antioxidants were also assessed in 24 stable COPD patients and 23 healthy control subjects. SOD and CAT activities in sputum were significantly increased in patients with AECOPD compared to those with stable disease (SOD: 0.142 [0.053-0.81] vs. 0.038 [0.002-0.146] U/mL, p < 0.01; CAT: 48.7 [18.7-72.6] vs. 10.2 [2.9-40.6] nmol/min/mL, p < 0.05), while treatment of exacerbation led to a decrease in enzyme activities (SOD: 0.094 [0.046-0.45] U/mL, p < 0.05; CAT: 28.0 [7.3-60.4] nmol/min/mL, p < 0.005). No changes were observed in the serum (p > 0.05). Both SOD and CAT activities significantly correlated with sputum neutrophil and lymphocyte cell counts in patients with AECOPD. Moreover, SOD and CAT values correlated with each other and also with sputum malondialdehyde, an established marker for oxidative stress. Our data demonstrate that sputum antioxidant activity is elevated during COPD exacerbation and suggest that activation of SODs and CAT is an integral part of the human defense mechanism against the increased oxidant production associated with AECOPD.

Defining the role of neutrophil-to-lymphocyte ratio in COPD: a systematic literature review

COPD is characterized by a pulmonary and systemic inflammatory process. Several authors have reported the elevation of multiple inflammatory markers in patients with COPD; however, their use in routine clinical practice has limitations. The neutrophil-to-lymphocyte ratio (NLR) is a useful and cost-effective inflammatory marker derived from routine complete blood count. We performed a systematic literature review using the PRISMA statement. Twenty-two articles were included, recruiting 7,601 COPD patients and 784 healthy controls. Compared with controls, COPD patients had significantly higher NLR values. We found a significant correlation between the NLR and clinical/functional parameters (FEV₁, mMRC, and BODE index) in COPD patients. Elevation of the NLR is associated with the diagnosis of acute exacerbation of COPD (pooled data propose a cut-off value of 3.34 with a median sensitivity, specificity, and area under the curve of 80%, 86%, and 0.86, respectively). Additionally, increased NLR is also associated with the diagnosis of a bacterial infection in exacerbated patients, with a cut-off value of 7.30, although with a low sensitivity and specificity. The NLR is an independent predictor of in-hospital and late mortality after exacerbation. In conclusion, the NLR could be a useful marker in COPD patients; however, further studies are needed to better identify the clinical value of the NLR.

Role of IL-32 Gamma on Bone Metabolism in Autoimmune Arthritis

IL-32 acts as a pro-inflammatory cytokine by inducing the synthesis of inflammatory molecules as well as promoting the morphological changes involved in the transformation of monocytes into osteoclasts (OCs). Evaluation of the functions of IL-32 has mainly focused on its inflammatory properties, such as involvement in the pathogenesis of various autoimmune diseases. Recently, IL-32 was shown to be involved in bone metabolism, in which it promotes the differentiation and activation of OCs and plays a key role in bone resorption in inflammatory conditions. IL-32γ also regulates bone formation in conditions such as ankylosing spondylitis and osteoporosis. In this review, we summarize the results of recent studies on the role of IL-32γ in bone metabolism in inflammatory arthritis.

Chronic obstructive pulmonary disease: MicroRNAs and exosomes as new diagnostic and therapeutic biomarkers

Chronic obstructive pulmonary disease (COPD) is known as a progressive lung disease and the fourth leading cause of death worldwide. Despite valuable efforts, there is still no accurate diagnostic and prognostic tool for COPD. Hence, it seems that finding new biomarkers could contribute to provide better therapeutic platforms for COPD patients. Among various biomarkers, microRNAs (miRNAs) have emerged as new biomarkers for the prognosis and diagnosis of patients with COPD. It has been shown that deregulation of miRNAs targeting a variety of cellular and molecular pathways such as Notch, Wnt, hypoxia-inducible factor-1α, transforming growth factor, Kras, and Smad could be involved in COPD pathogenesis. Multiple lines of evidence have indicated that extracellular vesicles such as exosomes could carry a variety of cargos (i.e., mRNAs, miRNAs, and proteins) which transfer various cellular and molecular signals to recipient cells. Here, we summarized various miRNAs which could be applied as diagnostic and prognostic biomarkers in the treatment of patients with COPD. Moreover, we highlighted the role of extracellular vesicles containing miRNAs as diagnostic and prognostic biomarkers in COPD patients.

Expression of Inflammatory Mediators in Induced Sputum: Comparative Study in Asthma and COPD

Asthma and COPD are the most common obstructive lung diseases characterized by inflammation in the lower airways which contribute to airflow limitation. Different inflammatory mediators are thought to play a key role in these diseases. This study was conducted in 13 patients with asthma, 12 patients with COPD, and 13 control subjects. The expression of mRNA of IL-6, IL-13, CXCL8, TSLP, IL-33, IL-25, IL-17, ECP, mast cell tryptase, CCL24, and CCL26 was assessed in induced sputum cells by real time PCR. We found that CXCL8 was strongly related to the neutrophil percentage but differed significantly in COPD and asthma patients. The expression of IL-17 was lower in patients with atopic asthma compared to non-atopic asthma. The percentage of macrophages correlated negatively with the expression of mast cell tryptase and ECP in COPD, and with CXCL8 in asthma. The expression of ECP correlated negatively with the severity of COPD symptoms measured by CAT. We conclude that asthma and COPD demonstrate a significant overlap in the airway cytokine profile. Thus, differentiation between the two diseases is difficult as based on a single cytokine, which suggests the coexistence of phenotypes sharing a common cytokine network in these obstructive lung diseases.

The Significance of Serum Interleukin-8 in Acute Exacerbations of Chronic Obstructive Pulmonary Disease

BACKGROUNDS

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is closely related to disease mortality. Systemic inflammation is considered to be involved in the pathogenesis of AECOPD. The current study aimed to investigate the clinical significance of the classic chemokine interleukin (IL)-8 in serum during AECOPD.

MATERIALS AND METHODS

In this current cross sectional, observational study, 50 patients with AECOPD, 25 patients with stable COPD and 25 healthy nonsmokers as the control group were selected. Clinical characteristics and spirometry data were collected. All patients were classified as grade 1-4 based on forced expiratory volume in 1 second (FEV1) after bronchodilation according to the GOLD severity classification and were divided into frequent exacerbation (FE) group (≥2 times/year) and non-frequent exacerbation (NFE) group (<1 time/year) according to acute exacerbation (AE) times in the previous 12 months before the visit. The serum IL-8, IL-6, tumor necrosis factor (TNF)-α, and superoxide dismutase levels were measured by the enzyme-linked immunosorbent assay technique.

RESULTS

Serum IL-8 levels increased sequentially from controls [9.45 pg/mL (ranged: 6.85-38.4)], to stable [51.60 pg/mL (ranged: 22.4-131.1)], and exacerbation stage [129 pg/mL (ranged: 57.7-374)]. The level of serum IL-8 was significant higher in patients with FE than that of patients with NFE (209.0 pg/mL (ranged: 115-472) vs 65.6 pg/mL (ranged: 11.2-149.3), P=0.008). A receiver operating characteristics curve (ROC) generated to evaluate IL-8, IL-6, and TNF-α levels to discriminate between patients with and without exacerbation showed that the total area under the curve (AUC) was 0.71 (95% confidence interval (CI): 0.5764-0.8381; P=0.003), 0.54 (95%CI: 0.4048-0.6943; P=0.54), and 0.52 (95%CI: 0.3912-0.6656; P= 0.7).

CONCLUSION

Serum IL-8 is a sensitive, easy-to-measure, and inexpensive biomarker to give an indication of the course of COPD during exacerbation, and is a target to be explored further as a predictor to distinguish the patients prone to exacerbation.

Tuberculosis State Is Associated with Expression of Toll-Like Receptor 2 in Sputum Macrophages

Mycobacterium tuberculosis is an intracellular pathogen that parasitizes the host macrophage. While approximately two billion people are infected worldwide, only 5 to 10% become diseased with pulmonary tuberculosis, at least in the absence of comorbidities. Tuberculosis control requires development of noninvasive methods probing the host immune status to help distinguish latent infection from active tuberculosis. With such methods, high-risk individuals could be targeted for treatment before disease manifestation. Previous investigations have been based on examination of peripheral blood cells or, more rarely, lung macrophages obtained with invasive procedures, such as bronchoalveolar lavages. Here we show that differences exist in the expression of a surface protein (Toll-like receptor 2) between macrophages recovered from the sputum of individuals in different diagnostic groups: i.e., infection free, latent tuberculosis infection, and active pulmonary tuberculosis. Thus, phenotypic analysis of local macrophages obtained with noninvasive procedures can help distinguish among tuberculosis infection stages.

During tuberculosis, macrophages are critical for both pathogen survival and host immune activation. Since expression of particular cell surface markers reflects cell function, we used flow cytometry to measure the abundance of surface markers associated with polarity, lipid uptake, or pattern recognition on macrophages found in induced sputum. Nine macrophage surface markers were examined from three groups of donors: infection-free, latent tuberculosis infection, and active pulmonary tuberculosis. Using a trend test, we found that expression of Toll-like receptor 2 was greater from absence of infection to latent infection and from latent infection to active tuberculosis. The results point to the possibility that innate immune cell phenotypes be used to distinguish among tuberculosis infection stages. Moreover, this study shows that readily accessible sputum macrophages have potential for tuberculosis diagnosis and prognosis.

IMPORTANCEMycobacterium tuberculosis is an intracellular pathogen that parasitizes the host macrophage. While approximately two billion people are infected worldwide, only 5 to 10% become diseased with pulmonary tuberculosis, at least in the absence of comorbidities. Tuberculosis control requires development of noninvasive methods probing the host immune status to help distinguish latent infection from active tuberculosis. With such methods, high-risk individuals could be targeted for treatment before disease manifestation. Previous investigations have been based on examination of peripheral blood cells or, more rarely, lung macrophages obtained with invasive procedures, such as bronchoalveolar lavages. Here we show that differences exist in the expression of a surface protein (Toll-like receptor 2) between macrophages recovered from the sputum of individuals in different diagnostic groups: i.e., infection free, latent tuberculosis infection, and active pulmonary tuberculosis. Thus, phenotypic analysis of local macrophages obtained with noninvasive procedures can help distinguish among tuberculosis infection stages.

Role of Proteases in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is generally associated with progressive destruction of airways and lung parenchyma. Various factors play an important role in the development and progression of COPD, like imbalance of proteases, environmental and genetic factors and oxidative stress. This review is specifically focused on the role of proteases and their imbalance in COPD. There are three classes (serine, mettalo, and cysteine) of proteases involved in COPD. In serine proteases, neutrophil elastase, cathepsin G, and proteinase-3 are involved in destruction of alveolar tissue. Matrix-mettaloproteinase-9, 12, 13, plays an influential role in severity of COPD. Among cysteine proteases, caspase-3, caspases-8 and caspase-9 play an important role in controlling apoptosis. These proteases activities can be regulated by inhibitors like α-1-antitrypsin, neutrophil elastase inhibitor, and leukocyte protease inhibitor. Studies suggest that neutrophil elastase may be a therapeutic target for COPD, and specific inhibitor against this enzyme has potential role to control the disease. Current study suggests that Dipeptidyl Peptidase IV is a potential marker for COPD. Since the expression of proteases and its inhibitors play an important role in COPD pathogenesis, therefore, it is worth investigating the role of proteases and their regulation. Understanding the biochemical basis of COPD pathogenesis using advanced tools in protease biochemistry and aiming toward translational research from bench-to-bedside will have great impact to deal with this health problem.

Identification of thyroxine-binding globulin as a candidate plasma marker of chronic obstructive pulmonary disease

Biomarkers for the management of chronic obstructive pulmonary disease (COPD) are limited. The aim of this study was to explore new plasma biomarkers in patients with COPD. Thyroxine-binding globulin (THBG) was initially identified by proteomics in a discovery panel and subsequently verified by enzyme-linked immunosorbent assay in another verification panel with a 1-year follow-up. THBG levels were elevated in patients with COPD (9.2±2.3 μg/mL) compared to those of the controls (6.6±2.0 μg/mL). Receiver operating characteristic curves suggested that THBG was able to slightly differentiate between patients with COPD and controls (area under the curve [AUC]: 0.814) and performed better if combined with fibrinogen (AUC: 0.858). THBG was more capable of distinguishing Global Initiative for Obstructive Lung Disease stages I–III and IV (AUC: 0.851) compared with fibrinogen (AUC 0.582). THBG levels were negatively associated with predicted percentage forced expiratory volume in 1 s and positively related to predicted percentage residual volume, RV/percentage total lung capacity, and percentage low-attenuation area. COPD patients with higher baseline THBG levels had a greater risk of acute exacerbation (AE) than those with lower THBG levels (P=0.014, by Kaplan–Meier curve; hazard ratio: 4.229, by Cox proportional hazards model). In summary, THBG is a potential plasma biomarker of COPD and can assist in the management of stable stage and AEs in COPD patients.

IL-8 predicts early mortality in patients with acute hypercapnic respiratory failure treated with noninvasive positive pressure ventilation

Background

Patients with Acute Hypercapnic Respiratory Failure (AHRF) who are unresponsive to appropriate medical treatment, are often treated with Noninvasive Positive Pressure Ventilation (NPPV). Clinical predictors of the outcome of this treatment are scarce. Therefore, we evaluated the role of the biomarkers IL-8 and GDF-15 in predicting 28-day mortality in patients with AHRF who receive treatment with NPPV.

Methods

The study population were 46 patients treated with NPPV for AHRF. Clinical and background data was registered and blood samples taken for analysis of inflammatory biomarkers. IL-8 and GDF-15 were selected for analysis, and related to risk of 28-day mortality (primary endpoint) using Cox proportional hazard models adjusted for gender, age and various clinical parameters.

Results

Of the 46 patients, there were 3 subgroup in regards to primary diagnosis: Acute Exacerbation of COPD (AECOPD, n = 34), Acute Heart Failure (AHF, n = 8) and Acute Exacerbation in Obesity Hypoventilation Syndrome (AEOHS, n = 4). There was significant difference in the basic characteristic of the subgroups, but not in the clinical parameters that were used in treatment decisions. 13 patients died within 28 days of admission (28%). The Hazard Ratio for 28-days mortality per 1-SD increment of IL-8 was 3.88 (95% CI 1.86–8.06, p < 0.001). When IL-8 values were divided into tertiles, the highest tertile had a significant association with 28 days mortality, HR 10.02 (95% CI 1.24–80.77, p for trend 0.03), compared with the lowest tertile. This correlation was maintained when the largest subgroup with AECOPD was analyzed. GDF-15 was correlated in the same way, but when put into the same model as IL-8, the significance disappeared.

Conclusion

IL-8 is a target to explore further as a predictor of 28 days mortality, in patients with AHRF treated with NPPV.

The asthma-COPD overlap syndrome: do we really need another syndrome in the already complex matrix of airway disease?

The term asthma–COPD overlap syndrome (ACOS) is one of multiple terms used to describe patients with characteristics of both COPD and asthma, representing ~20% of patients with obstructive airway diseases. The recognition of both sets of morbidities in patients is important to guide practical treatment decisions. It is widely recognized that patients with COPD and coexisting asthma present with a higher disease burden, despite the conceptual expectation that the “reversible” or “treatable” component of asthma would allow for more effective management and better outcomes. However, subcategorization into terms such as ACOS is complicated by the vast spectrum of heterogeneity that is encapsulated by asthma and COPD, resulting in different clinical clusters. In this review, we discuss the possibility that these different clusters are suboptimally described by the umbrella term “ACOS”, as this additional categorization may lead to clinical confusion and potential inappropriate use of resources. We suggest that a more clinically relevant approach would be to recognize the extreme variability and the numerous phenotypes encompassed within obstructive airway diseases, with various degrees of overlapping in individual patients. In addition, we discuss some of the evidence to be considered when making practical decisions on the treatment of patients with overlapping characteristics between COPD and asthma, as well as the potential options for phenotype and biomarker-driven management of airway disease with the aim of providing more personalized treatment for patients. Finally, we highlight the need for more evidence in patients with overlapping disease characteristics and to facilitate better characterization of potential treatment responders.

COPD biomarkers as tools for decision making in early clinical drug development

In this perspective article, we discuss, from a statistician's perspective, how biomarkers can be useful in decision making in drug development with emphasis on early clinical development (Phase I and II) in chronic obstructive pulmonary disease. We illustrate with examples of how biomarkers can affect the very choice of treatment strategy: for example, targeting patients in early versus late phases of the disease or patients with particular extrapulmonary manifestations of chronic obstructive pulmonary disease. We also illustrate the use of biomarkers for establishing proof of mechanism in Phase I trials and how surrogate biomarkers can be used as end points in Phase II leading to shorter and more efficient proof-of-principle and dose-finding trials.

[COPD: An early disease]

This general review deals with the mechanisms which underlie the genetic factors in COPD. Many cellular and biochemical mechanisms occur in bronchial inflammation. We present the experimental models of COPD, insisting on the importance of oxydative stress, and on recent knowledge about the lung microbiome. Starting from this pathophysiology basis, we show how various genetic targets are able to interfere with the disease model. Thanks to these genetic targets, new markers in exhaled breath condensates and new drug targets are rising.

Oxidative Stress Markers in Sputum

Although oxidative stress is thought to play a pivotal role in the pathogenesis of inflammatory airway diseases, its assessment in clinical practice remains elusive. In recent years, it has been conceptualized that oxidative stress markers in sputum should be employed to monitor oxidative processes in patients with asthma, chronic obstructive pulmonary disease (COPD), or cystic fibrosis (CF). In this review, the use of sputum-based oxidative markers was explored and potential clinical applications were considered. Among lipid peroxidation-derived products, 8-isoprostane and malondialdehyde have been the most frequently investigated, while nitrosothiols and nitrotyrosine may serve as markers of nitrosative stress. Several studies have showed higher levels of these products in patients with asthma, COPD, or CF compared to healthy subjects. Marker concentrations could be further increased during exacerbations and decreased along with recovery of these diseases. Measurement of oxidized guanine species and antioxidant enzymes in the sputum could be other approaches for assessing oxidative stress in pulmonary patients. Collectively, even though there are promising findings in this field, further clinical studies using more established detection techniques are needed to clearly show the benefit of these measurements in the follow-up of patients with inflammatory airway diseases.

Serum Metabolite Biomarkers Discriminate Healthy Smokers from COPD Smokers

COPD (chronic obstructive pulmonary disease) is defined by a fixed expiratory airflow obstruction associated with disordered airways and alveolar destruction. COPD is caused by cigarette smoking and is the third greatest cause of mortality in the US. Forced expiratory volume in 1 second (FEV1) is the only validated clinical marker of COPD, but it correlates poorly with clinical features and is not sensitive enough to predict the early onset of disease. Using LC/MS global untargeted metabolite profiling of serum samples from a well-defined cohort of healthy smokers (n = 37), COPD smokers (n = 41) and non-smokers (n = 37), we sought to discover serum metabolic markers with known and/or unknown molecular identities that are associated with early-onset COPD. A total of 1,181 distinct molecular ions were detected in 95% of sera from all study subjects and 23 were found to be differentially-expressed in COPD-smokers vs. healthy-smokers. These 23 putative biomarkers were differentially-correlated with lung function parameters and used to generate a COPD prediction model possessing 87.8% sensitivity and 86.5% specificity. In an independent validation set, this model correctly predicted COPD in 8/10 individuals. These serum biomarkers included myoinositol, glycerophopshoinositol, fumarate, cysteinesulfonic acid, a modified version of fibrinogen peptide B (mFBP), and three doubly-charged peptides with undefined sequence that significantly and positively correlate with mFBP levels. Together, elevated levels of serum mFBP and additional disease-associated biomarkers point to a role for chronic inflammation, thrombosis, and oxidative stress in remodeling of the COPD airways. Serum metabolite biomarkers offer a promising and accessible window for recognition of early-stage COPD.

Vasoactive Intestinal Peptide for Diagnosing Exacerbation in Chronic Obstructive Pulmonary Disease

BACKGROUND

Vasoactive intestinal peptide (VIP) is the most abundant neuropeptide in the lung. VIP has been linked to pulmonary arterial hypertension and hypoxia.

OBJECTIVES

We aimed to assess circulating VIP levels at exacerbation and at stable chronic obstructive pulmonary disease (COPD) and to evaluate the diagnostic performance in a well-characterized cohort of COPD patients.

METHODS

The nested cohort study included patients with Global Initiative for Chronic Obstructive Lung Disease stage II-IV. Patients were examined at stable state and at acute exacerbation of COPD (AE-COPD), and dedicated serum was collected at both conditions. Serum VIP levels were determined by enzyme-linked immunosorbent assay. Diagnostic accuracy was analyzed by receiver operating characteristic curve and area under the curve (AUC).

RESULTS

Patients with acute exacerbation (n = 120) and stable COPD (n = 163) had similar characteristics at baseline. Serum VIP levels did not correlate with oxygen saturation at rest (p = 0.722) or at exercise (p = 0.168). Serum VIP levels were significantly higher at AE-COPD (130.25 pg/ml, 95% CI 112.19-151.83) as compared to stable COPD (40.07 pg/ml, 95% CI 37.13-43.96, p < 0.001). The association of increased serum VIP with AE-COPD remained significant after propensity score matching (p < 0.001). Analysis of the Youden index indicated the optimal serum VIP cutoff value as 56.6 pg/ml. The probability of AE-COPD was very low if serum VIP was ≤35 pg/ml (sensitivity >90%) and very high if serum VIP was ≥88 pg/ml (specificity >90%). Serum VIP levels presented a robust performance to diagnose AE-COPD (AUC 0.849, 95% CI 0.779-0.899).

CONCLUSIONS

Increased serum VIP levels are associated with AE-COPD.

Measurement of C-reactive protein, procalcitonin and neutrophil elastase in saliva of COPD patients and healthy controls: correlation to self-reported wellbeing parameters

BACKGROUND

Saliva is increasingly promoted as an alternative diagnostic bio-sample to blood; however its role in respiratory disease requires elucidation. Our aim was to investigate whether C-reactive protein (CRP), procalcitonin (PCT) and neutrophil elastase (NE) could be measured in unstimulated whole saliva, and to explore differences between COPD patients and controls with normal lung function. We also determined the relationship between these salivary biomarkers and self-reported COPD-relevant metrics.

METHODS

Salivary CRP, PCT and NE levels were measured at each of 3 visits over a 14-day period alongside spirometry and a daily self-assessment dairy in 143 subjects: 20 never-smokers and 25 smokers with normal spirometry; 98 COPD patients [GOLD Stage I, 16; Stage II, 32; Stage III, 39; Stage IV, 11]. Twenty-two randomly selected subjects provided simultaneous blood samples.

RESULTS

Levels of each salivary biomarker could distinguish between the above cohorts. Significant differences remained for salivary CRP and NE (p < 0.05) following adjustment for age, gender, sampling time, gum disease and total co-morbidities; but not for BMI except for salivary NE, which remained higher in smokers compared to non-smokers and stable COPD subjects (p < 0.001). Patients with acute COPD exacerbations had a median increase in all 3 salivary biomarkers (p < 0.001); CRP: median 5.74 ng/ml, [interquartile range (IQR) 2.86-12.25], PCT 0.38 ng/ml, [IQR 0.22-0.94], and NE 539 ng/ml, [IQR 112.25-1264]. In COPD patients, only salivary CRP and PCT levels correlated with breathing scores (r = 0.14, p < 0.02; r = 0.13, p < 0.03 respectively) and sputum features but not with activities of daily living. Salivary CRP and PCT concentrations strongly correlated with serum counterparts [r = 0.82, (95% CI: 0.72-0.87), p < 0.001 by Spearman's; and r = 0.53, (95% CI: 0.33-0.69), p < 0.006 respectively]; salivary NE did not.

CONCLUSIONS

CRP, PCT and NE were reliably and reproducibly measured in saliva, providing clinically-relevant information on health status in COPD; additionally NE distinguished smoking status. All 3 salivary biomarkers increased during COPD exacerbations, with CRP and PCT correlating well with patient-derived clinical metrics. These results provide the conceptual basis for further development of saliva as a viable bio-sample in COPD monitoring and exacerbation management.

Biomarkers of progression of chronic obstructive pulmonary disease (COPD)

Disease progression of chronic obstructive pulmonary disease (COPD) is variable, with some patients having a relatively stable course, while others suffer relentless progression leading to severe breathlessness, frequent acute exacerbations of COPD (AECOPD), respiratory failure and death. Radiological markers such as CT emphysema index, bronchiectasis and coronary artery calcification (CAC) have been linked with increased mortality in COPD patients. Molecular changes in lung tissue reflect alterations in lung pathology that occur with disease progression; however, lung tissue is not routinely accessible. Cell counts (including neutrophils) and mediators in induced sputum have been associated with lung function and risk of exacerbations. Examples of peripheral blood biological markers (biomarkers) include those associated with lung function (reduced CC-16), emphysema severity (increased adiponectin, reduced sRAGE), exacerbations and mortality [increased CRP, fibrinogen, leukocyte count, IL-6, IL-8, and tumor necrosis factor α (TNF-α)] including increased YKL-40 with mortality. Emerging approaches to discovering markers of gene-environment interaction include exhaled breath analysis [volatile organic compounds (VOCs), exhaled breath condensate], cellular and systemic responses to exposure to air pollution, alterations in the lung microbiome, and biomarkers of lung ageing such as telomere length shortening and reduced levels of sirtuins. Overcoming methodological challenges in sampling and quality control will enable more robust yet easily accessible biomarkers to be developed and qualified, in order to optimise personalised medicine in patients with COPD.

Comparison of inflammatory markers in induced and spontaneous sputum in a cohort of COPD patients

BACKGROUND

Sputum induction is a non-invasive method for obtaining measurements of inflammation in the airways. Whether spontaneously sampled sputum can be a valid surrogate is unknown. The aim of this study was to compare levels of six inflammatory markers in sputum pairs consisting of induced and spontaneous sputum sampled on the same consultation either in a stable state or during exacerbations of chronic obstructive pulmonary disease (COPD).

METHODS

433 COPD patients aged 40-76, Global initiative for chronic Obstructive Lung Disease (GOLD) stage II-IV were enrolled in 2006/07 and followed every six months for three years. 356 patients were followed for potential exacerbations. Interleukin-6, interleukin-8, interleukin-18, interferon gamma-inducible protein-10, monokine induced by gamma interferon and tumor necrosis factor-alpha (IL-6, IL-8, IL-18, IP-10, MIG and TNF-α) were measured by bead based multiplex immunoassay in 60 paired sputum samples from 45 patients. Albumin was measured by enzyme immunoassay, for concentration correction. Culturing for bacterial growth was performed on 24 samples. Bland-Altman plots were used to assess agreement. The paired non-parametric Wilcoxon signed-rank test, the non-parametric Spearman's rank correlation test and Kruskal-Wallis test were used for statistical analyses. For all analyses, a p-value < 0.05 was considered significant.

RESULTS

Agreement between the two measurements was generally low for all six markers. TNF-α was significantly higher in spontaneous sputum at exacerbations (p = 0.002) and trending higher at the steady state (p = 0.06). Correlation coefficients between the levels of markers in induced and spontaneous sputum varied between 0.58 (IL-18) to 0.83 (IP-10). In spontaneous sputum IL-18 and MIG were higher in ex-smokers (p < 0.05). The levels of all markers were higher in GOLD stage III & IV except for IL-6 in spontaneous sputum and IL-18 in induced sputum, compared with GOLD stage II, although not statistically significant. In spontaneous sputum the levels of IL-6 were significantly higher if Haemophilus influenzae (HI) was not cultured.

CONCLUSION

We observed a low agreement and significant differences in inflammatory markers between induced and spontaneous sputum, both at steady state and exacerbations. We recommend considering sampling method when reporting on inflammatory markers in sputum.