Biomarker surrogates do not accurately predict sputum eosinophil and neutrophil percentages in asthmatic subjects

Approaches to the assessment of severe asthma: barriers and strategies

Asthma is a chronic condition with great variability. It is characterized by intermittent episodes of wheeze, cough, chest tightness, dyspnea and backed by variable airflow limitation, airway inflammation and airway hyper-responsiveness. Asthma severity varies uniquely between individuals and may change over time. Stratification of asthma severity is an integral part of asthma management linking appropriate treatment to establish asthma control. Precision assessment of severe asthma is crucial for monitoring the health of people with this disease. The literature suggests multiple factors that impede the assessment of severe asthma, these can be grouped into health care professional, patient and organizational related barriers. These barriers do not exist in isolation but interact and influence one another. Recognition of these barriers is necessary to promote precision in the assessment and management of severe asthma in the era of targeted therapy. In this review, we discuss the current knowledge of the barriers that impede assessment in severe asthma and recommend potential strategies for overcoming these barriers. We highlight the relevance of multidimensional assessment as an ideal approach to the assessment and management of severe asthma.

Understanding Asthma Phenotypes, Endotypes, and Mechanisms of Disease

The model of asthma as a single entity has now been replaced by a much more complex biological network of distinct and interrelating inflammatory pathways. The term asthma is now considered an umbrella diagnosis for several diseases with distinct mechanistic pathways (endotypes) and variable clinical presentations (phenotypes). The precise definition of these endotypes is central to asthma management due to inherent therapeutic and prognostic implications. This review presents the molecular mechanisms behind the heterogeneity of airway inflammation in asthmatic patients. Asthma endotypes may be broadly regarded as type 2 (T2) high or T2-low. Several biologic agents have been approved for T2-high asthma, with numerous other therapeutics that are incipient and similarly targeted at specific molecular mechanisms. Collectively, these advances have shifted existing paradigms in the approach to asthma to tailor novel therapies.

Asthma in Children and Adults-What Are the Differences and What Can They Tell us About Asthma?

Asthma varies considerably across the life course. Childhood asthma is known for its overall high prevalence with a male predominance prior to puberty, common remission, and rare mortality. Adult asthma is known for its female predominance, uncommon remission, and unusual mortality. Both childhood and adult asthma have variable presentations, which are described herein. Childhood asthma severity is associated with duration of asthma symptoms, medication use, lung function, low socioeconomic status, racial/ethnic minorities, and a neutrophilic phenotype. Adult asthma severity is associated with increased IgE, elevated FeNO, eosinophilia, obesity, smoking, and low socioeconomic status. Adult onset disease is associated with more respiratory symptoms and asthma medication use despite higher prebronchodilator FEV1/FVC. There is less quiescent disease in adult onset asthma and it appears to be less stable than childhood-onset disease with more relapses and less remissions.

Current and future targeted therapies for severe asthma: Managing treatment with biologics based on phenotypes and biomarkers

Asthma is a respiratory disorder with considerable heterogeneity in aetiology, triggers, clinical characteristics and response to therapy. This diversity reflects different inflammatory pathways that can be subdivided into clinically similar categories called phenotypes, or pathogenically comparable groups called endotypes. In recent years, a great amount of research has been dedicated to the investigation and understanding of the heterogeneity of asthma pathophysiology and to the identification of treatable traits, biomarkers, mediators and therapeutic targets. Severe asthma is defined as an uncontrolled disease despite a maximal conventional therapeutic approach. While, to date, some target therapies showing improvements in lung function, asthma symptoms and a reduction of the annual rate of exacerbations in patients with severe asthma have been already approved, other treatments are currently being studied, specifically targeting Type 2 asthma. Further progress however, is still needed to tackle the molecular pathways for non-Type 2 asthma. The aim of the present narrative review is to discuss and examine the indication, mechanisms of action and therapeutic effects of currently available and emerging biologic agents for the treatment of severe asthma.

Extracellular DNA, Neutrophil Extracellular Traps, and Inflammasome Activation in Severe Asthma

Rationale: Extracellular DNA (eDNA) and neutrophil extracellular traps (NETs) are implicated in multiple inflammatory diseases. NETs mediate inflammasome activation and IL-1β secretion from monocytes and cause airway epithelial cell injury, but the role of eDNA, NETs, and IL-1β in asthma is uncertain. Objectives: To characterize the role of activated neutrophils in severe asthma through measurement of NETs and inflammasome activation. Methods: We measured sputum eDNA in induced sputum from 399 patients with asthma in the Severe Asthma Research Program-3 and in 94 healthy control subjects. We subdivided subjects with asthma into eDNA-low and -high subgroups to compare outcomes of asthma severity and of neutrophil and inflammasome activation. We also examined if NETs cause airway epithelial cell damage that can be prevented by DNase. Measurements and Main Results: We found that 13% of the Severe Asthma Research Program-3 cohort is "eDNA-high," as defined by sputum eDNA concentrations above the upper 95th percentile value in health. Compared with eDNA-low patients with asthma, eDNA-high patients had lower Asthma Control Test scores, frequent history of chronic mucus hypersecretion, and frequent use of oral corticosteroids for maintenance of asthma control (all P values <0.05). Sputum eDNA in asthma was associated with airway neutrophilic inflammation, increases in soluble NET components, and increases in caspase 1 activity and IL-1β (all P values <0.001). In in vitro studies, NETs caused cytotoxicity in airway epithelial cells that was prevented by disruption of NETs with DNase. Conclusions: High extracellular DNA concentrations in sputum mark a subset of patients with more severe asthma who have NETs and markers of inflammasome activation in their airways.

Biomarkers and asthma management: analysis and potential applications

PURPOSE OF REVIEW

Asthma features a high degree of heterogeneity in both pathophysiology and therapeutic response, resulting in many asthma patients being treated inadequately. Biomarkers indicative of underlying pathological processes could be used to identify disease subtypes, determine prognosis and to predict or monitor treatment response. However, the newly identified as well as more established biomarkers have different applications and limitations.

RECENT FINDINGS

Conventional markers for type 2-high asthma, such as blood eosinophils, fraction of exhaled nitric oxide, serum IgE and periostin, feature limited sensitivity and specificity despite their significant correlations. More distinctive models have been developed by combining biomarkers and/or using omics techniques. Recently, a model with a positive predictive value of 100% for identification of type 2-high asthma based on a combination of minimally invasive biomarkers was developed.

SUMMARY

Individualisation of asthma treatment regimens on the basis of biomarkers is necessary to improve asthma control. However, the suboptimal properties of currently available conventional biomarkers limit its clinical utility. Newly identified biomarkers and models based on combinations and/or omics analysis must be validated and standardised before they can be routinely applied in clinical practice. The development of robust biomarkers will allow development of more efficacious precision medicine-based treatment approaches for asthma.

The prevalence and disease burden of severe eosinophilic asthma in Japan

Background: There are limited data on the prevalence and burden of severe eosinophilic asthma (SEA) both in Japan and globally. This study aimed to assess the prevalence and burden of SEA in Japan. Methods: This study was a retrospective, observational cohort analysis using health records or health insurance claims from patients with severe asthma treated at Kyoto University Hospital. The primary outcome was the prevalence of SEA, defined as a baseline blood eosinophil count ≥300 cells/μL. Secondary outcomes included frequency and risk factors of asthma exacerbations, and asthma-related healthcare resource utilization and costs. Results: Overall, 217 patients with severe asthma were included; 160 (74%) had eosinophil assessments. Of these, 97cases (61%), 54cases (34%), and 33cases (21%) had a blood eosinophil count ≥150, ≥300, and ≥500 cells/μL, respectively. Proportion of SEA was 34%. Blood eosinophil count was not associated with a significantly increased frequency of exacerbations. In the eosinophilic group, lower % forced expiratory volume in 1 second and higher fractional exhaled nitric oxide were predictive risk factors, while the existence of exacerbation history was a predictive risk factor for asthma exacerbations in the non-eosinophilic group. Severe asthma management cost was estimated as ¥357,958/patient-year, and asthma exacerbations as ¥26,124/patient-year. Conclusions: Approximately, one-third of patients with severe asthma in Japan have SEA. While risk factors for exacerbations differed between SEA and severe non-eosinophilic asthma, both subgroups were associated with substantial disease and economic burden. From subgroup analysis, blood eosinophil counts could be an important consideration in severe asthma management.

Are high- and low-molecular-weight sensitizing agents associated with different clinical phenotypes of occupational asthma?

BACKGROUND

High-molecular-weight (HMW) proteins and low-molecular-weight (LMW) chemicals can cause occupational asthma (OA) although few studies have thoroughly compared the clinical, physiological, and inflammatory patterns associated with these different types of agents. The aim of this study was to determine whether OA induced by HMW and LMW agents shows distinct phenotypic profiles.

METHODS

Clinical and functional characteristics, and markers of airway inflammation were analyzed in an international, multicenter, retrospective cohort of subjects with OA ascertained by a positive inhalation challenge response to HMW (n = 544) and LMW (n = 635) agents.

RESULTS

Multivariate logistic regression analysis showed significant associations between OA caused by HMW agents and work-related rhinitis (OR [95% CI]: 4.79 [3.28-7.12]), conjunctivitis (2.13 [1.52-2.98]), atopy (1.49 [1.09-2.05]), and early asthmatic reactions (2.86 [1.98-4.16]). By contrast, OA due to LMW agents was associated with chest tightness at work (2.22 [1.59-3.03]), daily sputum (1.69 [1.19-2.38]), and late asthmatic reactions (1.52 [1.09-2.08]). Furthermore, OA caused by HMW agents showed a higher risk of airflow limitation (1.76 [1.07-2.91]), whereas OA due to LMW agents exhibited a higher risk of severe exacerbations (1.32 [1.01-1.69]). There were no differences between the two types of agents in the baseline sputum inflammatory profiles, but OA caused by HMW agents showed higher baseline blood eosinophilia and a greater postchallenge increase in fractional nitric oxide.

CONCLUSION

This large cohort study describes distinct phenotypic profiles in OA caused by HMW and LMW agents. There is a need to further explore differences in underlying pathophysiological pathways and outcome after environmental interventions.

Daily patient-reported health status assessment improvements with benralizumab for patients with severe, uncontrolled eosinophilic asthma

Background

Patients with severe, uncontrolled asthma experience debilitating symptoms that result in meaningful reductions to health-related quality of life. Benralizumab is an interleukin-5 receptor alpha–directed cytolytic monoclonal antibody that reduces exacerbations and improves asthma symptoms for patients with severe, uncontrolled eosinophilic asthma.

Objective

The objective of this study was to evaluate improvements in daily asthma-related health status outcomes following treatment with benralizumab.

Methods

Pooled results from the SIROCCO (NCT01928771) and CALIMA (NCT01914757) Phase III studies were analyzed. Patients aged 12–75 years with severe, uncontrolled asthma, and blood eosinophil counts (BEC) ≥300 and ≥150 cells/µL were evaluated. Patients received subcutaneous benralizumab 30 mg every 4 weeks (Q4W) or every 8 weeks (Q8W, first three doses Q4W) or placebo and completed a daily diary reporting rescue medication use, night-time awakening requiring rescue medication use, perceived tiredness, and asthma-related activity impairment. Outcome measures were compared across treatment arms from baseline to end of treatment (EOT) using a mixed-effect model for repeated measures analyses.

Results

Patients with BEC ≥300 cells/µL receiving benralizumab Q8W had greater improvements in all patient-reported outcomes at EOT relative to baseline than patients receiving placebo (all nominal P≤0.013). Effects were reported as early as 3 days following the initial dose and sustained throughout treatment for daily and night-time rescue medication use and night-time awakenings requiring rescue medication. For patients with BEC ≥300 and ≥150 cells/ µL, sustained improvements in activity impairment items (all nominal P<0.05) were achieved with benralizumab Q8W at week 2.

Conclusion

Benralizumab produces sustained reductions by as early as 3 days in rescue medication use and activity impairment for patients with severe, uncontrolled eosinophilic asthma.

Variability of blood eosinophils in patients in a clinic for severe asthma

BACKGROUND

Blood eosinophils are used to determine eligibility for agents targeting IL-5 in patients with uncontrolled asthma. However, little is known about the variability of blood eosinophil measures in these patients before treatment initiation.

OBJECTIVE

To characterize variability and patterns of variability of blood eosinophil levels in a real-world clinic for severe asthmatics.

METHODS

Retrospective review of blood eosinophils measured over a 5-year period in patients enrolled in an urban clinic. Repeated measures of blood eosinophil levels in individuals were evaluated, and cluster analysis was performed to characterize patients by eosinophil patterns. Clinical characteristics associated with eosinophil levels and patterns of variability were analysed.

RESULTS

Patients treated in the Bellevue Hospital Asthma Clinic within a 3-month period were identified (n = 219). Blood eosinophil measures were obtained over the previous 5 years. Only 6% (n = 13) of patients had levels that were consistently above 300 cells/μL. Nearly 50% (n = 104) had eosinophil levels that traversed the threshold of 300 cells/μL. In contrast, 102 (46%) had levels that never reached the threshold of 300 cells/μL. Cluster analyses revealed three clusters with differing patterns of levels and variability. There was a suggestion of decreased clinical control and increased atopy in the cluster with the greatest variability in blood eosinophil measures.

CONCLUSION

In an urban clinic for patients referred for uncontrolled asthma, blood measures of eosinophils were variable and showed differing patterns of variability. These data reinforce the need to perform repeated eosinophil blood measures for appropriate designation for therapeutic intervention.

Serum Levels of Eosinophil-Derived Neurotoxin: A Biomarker for Asthma Severity in Adult Asthmatics

Purpose

Eosinophilic inflammation is a key component of severe asthma (SA). However, there has been no reliable serum biomarker for the eosinophilic inflammation of SA. We hypothesized that serum eosinophil-derived neurotoxin (EDN) could predict the eosinophilic inflammation of SA in adult asthmatics.

Methods

Severe asthmatics (n = 235), nonsevere asthmatics (n = 898), and healthy controls (n = 125) were enrolled from Ajou University Hospital, South Korea. The serum levels of EDN and periostin were measured by enzyme-linked immunosorbent assay and compared between severe and nonsevere asthmatics. Their associations with total eosinophil count (TEC) and clinical parameters were evaluated; clinical validation of the K-EDN kit for the measurement of serum EDN was evaluated.

Results

Severe asthmatics were older and had longer disease duration with significantly lower levels of forced expiratory volume in 1 second and methacholine PC20 than nonsevere asthmatics. Significant differences were found in TEC or sputum eosinophil count (%) between the groups. The serum levels of EDN and periostin were significantly higher in severe asthmatics than in nonsevere asthmatics and in healthy controls (all P < 0.05). Although significant correlations were found between serum EDN levels measured by the 2 kits (ρ = 0.545, P < 0.0001), higher correlation coefficients between serum EDN levels measured by the K-EDN kit and TEC were higher (ρ = 0.358, P < 0.0001) than those between serum EDN levels measured by the MBL kit and TEC (ρ = 0.319, P < 0.0001) or serum periostin level (ρ = 0.222, P < 0.0001). Multivariate regression analysis demonstrated that serum EDN levels measured by the K-EDN kit predicted the phenotype of SA (P = 0.003), while 2 other biomarkers did not.

Conclusions

The serum EDN level may be a useful biomarker for assessing asthma severity in adult asthmatics.

Recent developments and highlights in biomarkers in allergic diseases and asthma

The potential of precision medicine in allergy and asthma has only started to be explored. A significant clarification in the pathophysiology of rhinitis, chronic rhinosinusitis, asthma, food allergy and drug hypersensitivity was made in the last decade. This improved understanding led to a better classification of the distinct phenotypes and to the discovery of new drugs such as biologicals, targeting phenotype-specific mechanisms. Nevertheless, many conditions remain poorly understood such as non-eosinophilic airway diseases or non-IgE-mediated food allergy. Moreover, there is a need to predict the response to specific therapies and the outcome of drug and food provocations. The identification of patients at risk of progression towards severity is also an unmet need in order to establish adequate preventive or therapeutic measures. The implementation of precision medicine in the clinical practice requires the identification of phenotype-specific markers measurable in biological matrices. To become useful, these biomarkers need to be quantifiable by reliable systems, and in samples obtained in an easy, rapid and cost-efficient way. In the last years, significant research resources have been put in the identification of valid biomarkers for asthma and allergic diseases. This review summarizes these recent advances with focus on the biomarkers with higher clinical applicability.

[Vasculitides and eosinophilic pulmonary diseases]

Eosinophilic granulocytes form peripheral effector cells controlled by Th2 lymphocytes, which cause local cell, tissue, and functional disorders of infiltrated organs via the release of cytotoxic basic proteins and oxygen radicals. Diseases associated with eosinophilia include systemic and organ-related forms. The lungs are involved in eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as Churg-Strauss syndrome), acute and chronic eosinophilic pneumonia, as well as in an organ manifestation in hypereosinophilic syndrome and certain parasitic diseases. In particular, the lungs are frequently affected in vasculitis of small vessels, including EGPA, granulomatosis with polyangiitis (GPA), and microscopic polyangiitis (MPA). Among these, EGPA is the most frequent pulmonary eosinophil vasculitis representative. In addition, there are various overlap syndromes in which characteristic features of EGPA can be detected in the context of other anti-neutrophil cytoplasmic antibody (ANCA-)associated vasculitides. Occasionally, non-ANCA-associated pulmonary vasculitides occur with eosinophilia (e.g., Schönlein-Henoch purpura, Kawasaki disease, drug-induced hypersensitivity, and paraneoplastic syndrome). Herein, the pulmonary vasculitides accompanying eosinophilia are presented with respect to both the lung manifestations and pulmonary eosinophilia.

Baseline patient factors impact on the clinical efficacy of benralizumab for severe asthma

Benralizumab is an anti-eosinophilic monoclonal antibody that reduces exacerbations and improves lung function for patients with severe, uncontrolled asthma with eosinophilic inflammation. We evaluated the impact of baseline factors on benralizumab efficacy for patients with severe asthma.

This analysis used pooled data from the SIROCCO (ClinicalTrials.gov identifier NCT01928771) and CALIMA (ClinicalTrials.gov identifier NCT01914757) Phase III studies. Patients aged 12–75 years with severe, uncontrolled asthma receiving high-dosage inhaled corticosteroids plus long-acting β₂-agonists received benralizumab 30 mg subcutaneously every 8 weeks (Q8W, first three doses every 4 weeks (Q4W)), Q4W or placebo. Baseline factors that influenced benralizumab efficacy were evaluated, including oral corticosteroid (OCS) use, nasal polyposis, pre-bronchodilator forced vital capacity (FVC), prior year exacerbations and age at diagnosis. Efficacy outcomes included annual exacerbation rate and change in pre-bronchodilator forced expiratory volume in 1 s at treatment end relative to placebo.

Benralizumab Q8W treatment effect was enhanced with each baseline factor for all patients and those with ≥300 eosinophils·μL⁻¹ relative to the overall population. OCS use, nasal polyposis and FVC <65% of predicted were associated with greater benralizumab Q8W responsiveness for reduced exacerbation rate for patients with <300 eosinophils·μL⁻¹.

Baseline clinical factors and blood eosinophil counts can help identify patients potentially responsive to benralizumab.

Key baseline factors can aid in identifying patients who may respond to benralizumabhttp://ow.ly/uPVX30ltHTF

Comparative Efficacy of Anti IL-4, IL-5 and IL-13 Drugs for Treatment of Eosinophilic Asthma: A Network Meta-analysis

BACKGROUND

Several new biologics have been studied in patients with eosinophilic asthma with varying degrees of response on clinical outcomes. No head-to-head trial has directly compared the efficacy of these drugs.

OBJECTIVE

To synthesize data on the relative efficacy of benralizumab, dupilumab, lebrikizumab, mepolizumab, reslizumab, and tralokinumab using network meta-analysis.

DATA SOURCES

We searched PubMed from inception to December 15th, 2017.

DATA EXTRACTION AND SYNTHESIS

We used the 'frequentist' methodology with random effect models using primarily 'netmeta' function in R to generate network meta-analysis results. Outcomes assessed included changes in forced expiratory volume-in 1 s (FEV1), asthma control questionnaire (ACQ), and asthma quality of life questionnaire (AQLQ). We also separately analyzed the annualized rate ratios for asthma exacerbations for each drug and compared to placebo. For all outcomes assessed, all drugs were superior to placebo except tralokinumab. In terms of magnitude of effect, dupilumab, followed by reslizumab and benralizumab showed the greatest increase in FEV1, 0.16L (95% CIs: 0.08-0.24), 0.13L (0.10-0.17), and 0.12L (0.08-0.17), compared to placebo. While mepolizumab, followed by dupliumab, benralizumab, and reslizumab showed reductions in ACQ scores, in order of magnitude of effect, dupilumab, followed by mepolizumab, benralizumab, and reslizumab showed the greatest increase in AQLQ scores. All drugs decreased asthma exacerbations but the results were only significant for reslizumab and dupilumab.

CONCLUSIONS

All drugs except for tralokinumab showed improvements in FEV1, ACQ, and AQLQ. Only reslizumab and dupilumab were associated with statistically significant reductions in asthma exacerbation rates.

Serum sST2 levels predict severe exacerbation of asthma

BACKGROUND

Neutrophilic inflammation is associated with poorly controlled asthma. Serum levels of sST2, a soluble IL-33 receptor, increase in neutrophilic lung diseases. We hypothesized that high serum sST2 levels in stable asthmatics are a predictor for exacerbation within a short duration.

METHODS

This prospective observational study evaluated the serum sST2 levels of 104 asthmatic patients who were treated by a lung disease specialist with follow-ups for 3 months.

RESULTS

High serum sST2 levels (> 18 ng/ml) predicted severe asthma exacerbation within 3 months. Serum sST2 levels correlated positively with asthma severity (treatment step), airway H2O2 levels, and serum IL-8 levels. High serum sST2 levels and blood neutrophilia (> 6000 /μl) were independent predictors of exacerbation. We defined a post-hoc exacerbation-risk score combining high serum sST2 level and blood neutrophilia, which stratified patients into four groups. The score predicted exacerbation-risk with an area under curve of 0.91 in the receiver operating characteristic curve analysis. Patients with the highest scores had the most severe phenotype, with 85.7% showing exacerbation, airflow limitation, and corticosteroid-insensitivity.

CONCLUSIONS

High serum sST2 levels predicted exacerbation within the general asthmatic population and, when combined with blood neutrophil levels, provided an exacerbation-risk score that was an accurate predictor of exacerbation occurring within 3 months.

Implication of fraction of exhaled nitric oxide and blood eosinophil count in severe asthma

BACKGROUND

Severe asthma is a complex disease with heterogeneous features and involves type 2 airway inflammation, including eosinophil accumulation. Surrogate biomarkers, fraction of exhaled nitric oxide (FeNO) and blood eosinophil count (b-EOS), may predict eosinophilic airway inflammation. Here we investigated clinical characteristics of severe asthma phenotype using a combined analysis of FeNO and b-EOS.

METHODS

This retrospective study examined clinical data of patients with severe asthma (N = 107; median age, 64 years) treated at Saitama Medical University Hospital from 2009 to 2016. Thresholds of FeNO and b-EOS for sputum eosinophil ratio ≥2% were determined using receiver operating characteristic curve (ROC) analysis. Clinical characteristics were analyzed after classifying patients into four subgroups according to these thresholds.

RESULTS

Of 39 induced sputum samples examined, ROC area under the curve for predicting sputum eosinophilia was 82.0% (p = 0.001) for b-EOS and 77.0% (p = 0.006) for FeNO at optimal cut-off values of ≥300/μL and ≥25 ppb, respectively. The number of sensitized allergens was higher in the high FeNO/low b-EOS and high FeNO/high b-EOS subgroups (p < 0.05). The prevalence of chronic sinusitis was higher in the low FeNO/high b-EOS and high FeNO/high b-EOS subgroups (p = 0.04). The high FeNO/high b-EOS subgroup included the largest proportion (approximately 40%) of patients experiencing frequent severe exacerbations. Both low FeNO/low b-EOS and high FeNO/low b-EOS subgroups showed less severe exacerbations.

CONCLUSIONS

Combined evaluation of FeNO and b-EOS can identify patients with frequent exacerbations and stratify the appropriate therapy for type 2 inflammation-predominant severe asthma.

Use of biomarkers to identify phenotypes and endotypes of severeasthma

OBJECTIVE

Severe asthma can be classified into phenotypes and endotypes, which may inform clinicians about inflammatory pathways leading to disease and ultimately guide optimal therapeutic strategy. Biomarkers, objectively measurable characteristics of the disease, are of increasing interest to clinicians and researchers as powerful tools to distinguish among the severe asthma phenotypes and endotypes. The objective of this review is to highlight current knowledge of biomarker applications to identify phenotypes and endotypes of severe asthma.

DATA SOURCES

Sources used include observational cohorts, clinical trials, translational studies, comprehensive reviews, and expert/taskforce statements.

STUDY SELECTIONS

Included studies were selected for their relevance to the topic and for strength of data or study design.

RESULTS

In severe asthma, biomarkers can be used for diagnosis of phenotype or endotype, can also be predictive of clinical outcomes or response to therapy, and may be dynamic with time or therapy. Fully determining phenotype or endotype of severe asthma will require interpretation of combinations of commercially available biomarkers.

CONCLUSION

Biomarkers have multiple potential clinical applications in severe asthma. Novel biomarkers may add accuracy to this field.

Sputum cytology during late-phase responses to inhalation challenge with different allergens

BACKGROUND

In mouse models of allergic asthma, exposure to different allergens can trigger distinct inflammatory subtypes in the airways. We investigated whether this observation extends to humans.

METHODS

We compared the frequency of sputum inflammatory subtypes between mild allergic asthma subjects (n = 129) exposed to different allergens in inhalation challenge tests. These tests were performed using a standardized protocol as part of clinical trials of experimental treatments for asthma, prior to drug randomization. Five allergen types were represented: the house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae, ragweed, grass, and cat.

RESULTS

Of 118 individuals with a sputum sample collected before allergen challenge (baseline), 45 (38%) had paucigranulocytic, 51 (43%) eosinophilic, 11 (9%) neutrophilic, and 11 (9%) mixed granulocytic sputum. Of note, most individuals with baseline paucigranulocytic sputum developed eosinophilic (48%) or mixed granulocytic (43%) sputum 7 hours after allergen challenge, highlighting the dynamic nature of sputum inflammatory subtype in asthma. Overall, there was no difference in the frequency of sputum inflammatory subtypes following challenge with different allergen types. Similar results were observed at 24 hours after allergen challenge.

CONCLUSIONS

Unlike reported in mice, in humans the sputum inflammatory subtype observed after an allergen-induced asthma exacerbation is unlikely to be influenced by the type of allergen used.

Association between blood eosinophil count with asthma hospital readmissions

INTRODUCTION

The presence of eosinophils in asthma inflammation is a relevant factor in the pathophysiology of the disease, however the relationship between the blood eosinophil count (BEC) with asthma severity and prognosis is still under debate. The aim of this work is to analyze the relationship between the BEC levels and hospital readmissions in patients with asthma.

MATERIAL AND METHODS

A review was retrospectively carried out on all admissions of patients over 18 years old due to exacerbation of asthma occurring in our hospital between the years 2000 and 2010. The personal characteristics and the asthma personal history of each patient were recorded. The BEC was determined from the first blood sample taken from the patient after their arrival at the hospital. Hospital early, late and frequent readmissions were analyzed using 4 cut-off points; less than 150 eosinophils/μL vs ≥150/μL, less than 200 vs 200 /μL, less than 300 vs ≥300/μL, and less than 400 vs ≥400/μL.

RESULTS

We have included 1316 patients, 70% of whom are women, as well as a mean age of 60 years, and a mean FEV1 of 73.5% of the reference value. The mean eosinophil blood count was 201.7 cells/μL. A BEC ≥300 cells/μL showed a reduction of risk of late readmission of 42%, a BEC ≥400 cells/μL showed a reduction in late readmission risk of 41% and decrease in frequent late readmission of 63%.

CONCLUSIONS

Our study appears to support that an elevated BEC is associated with a lower incidence of asthma hospital readmissions.

Paucigranulocytic asthma: Uncoupling of airway obstruction from inflammation

Among patients with asthma, heterogeneity exists regarding the pattern of airway inflammation and response to treatment, prompting the necessity of recognizing specific phenotypes. Based on the analysis of inflammatory cell counts in induced sputum, asthmatic patients can be classified into 4 unique phenotypes: eosinophilic asthma, neutrophilic asthma, mixed granulocytic asthma, and paucigranulocytic asthma (PGA). PGA is an asthma phenotype with no evidence of increased numbers of eosinophils or neutrophils in sputum or blood and in which anti-inflammatory therapies are ineffective at controlling symptoms. Although underinvestigated, PGA is the most common asthma phenotype in patients with stable asthma. However, PGA is sometimes underestimated because of the exclusive reliance on induced sputum cell counts, which are variable among cohorts of studies, prompting the necessity of developing improved biomarkers. Importantly, investigators have reported that inhaled corticosteroids had a limited effect on airway inflammatory markers in patients with PGA and therefore defining PGA as a potentially "steroid-insensitive" phenotype that requires exploration of alternative therapies. PGA manifests as an uncoupling of airway obstruction from airway inflammation that can be driven by structural changes within the airways, such as airway smooth muscle tissue hypertrophy. Animal models provide evidence that processes evoking airway hyperresponsiveness and airway smooth muscle thickening occur independent from inflammation and might be a consequence of a loss of negative homeostatic processes. Collectively, further understanding of PGA with a focus on the characterization, prevalence, clinical significance, and pathobiology derived from animal studies will likely provide precision therapies that will improve PGA clinical outcomes.

Asthma Endotyping and Biomarkers in Childhood Asthma

Childhood asthma represents a heterogeneous challenging disease, in particular in its severe forms. The identification of different asthma phenotypes has stimulated research in underlying molecular mechanisms, such as the endotypes, and paved the way to the search for related specific biomarkers, which may guide diagnosis, management, and predict response to treatment. A limited number of biomarkers are currently available in clinical practice in the pediatric population, mostly reflecting type 2-high airway inflammation. The identification of biomarkers of childhood asthma is an active area of research that holds a potential great clinical utility and may represent a step forward toward tailored management and therapy: the so-called Precision Medicine. The aim of the present review is to provide an updated overview of asthma endotyping, mostly focusing on novel noninvasive biomarkers in childhood asthma.

Large-Scale Label-Free Quantitative Mapping of the Sputum Proteome

Analysis of induced sputum supernatant is a minimally invasive approach to study the epithelial lining fluid and, thereby, provide insight into normal lung biology and the pathobiology of lung diseases. We present here a novel proteomics approach to sputum analysis developed within the U-BIOPRED (unbiased biomarkers predictive of respiratory disease outcomes) international project. We present practical and analytical techniques to optimize the detection of robust biomarkers in proteomic studies. The normal sputum proteome was derived using data-independent HDMS^E applied to 40 healthy nonsmoking participants, which provides an essential baseline from which to compare modulation of protein expression in respiratory diseases. The "core" sputum proteome (proteins detected in ≥40% of participants) was composed of 284 proteins, and the extended proteome (proteins detected in ≥3 participants) contained 1666 proteins. Quality control procedures were developed to optimize the accuracy and consistency of measurement of sputum proteins and analyze the distribution of sputum proteins in the healthy population. The analysis showed that quantitation of proteins by HDMS^E is influenced by several factors, with some proteins being measured in all participants' samples and with low measurement variance between samples from the same patient. The measurement of some proteins is highly variable between repeat analyses, susceptible to sample processing effects, or difficult to accurately quantify by mass spectrometry. Other proteins show high interindividual variance. We also highlight that the sputum proteome of healthy individuals is related to sputum neutrophil levels, but not gender or allergic sensitization. We illustrate the importance of design and interpretation of disease biomarker studies considering such protein population and technical measurement variance.

Having concomitant asthma phenotypes is common and independently relates to poor lung function in NHANES 2007-2012

Background

Evidence for distinct asthma phenotypes and their overlap is becoming increasingly relevant to identify personalized and targeted therapeutic strategies. In this study, we aimed to describe the overlap of five commonly reported asthma phenotypes in US adults with current asthma and assess its association with asthma outcomes.

Methods

Data from the National Health and Nutrition Examination Surveys (NHANES) 2007-2012 were used (n = 30,442). Adults with current asthma were selected. Asthma phenotypes were: B-Eos-high [if blood eosinophils (B-Eos) ≥ 300/mm³]; FeNO-high (FeNO ≥ 35 ppb); B-Eos&FeNO-low (B-Eos < 150/mm³ and FeNO < 20 ppb); asthma with obesity (AwObesity) (BMI ≥ 30 kg/m²); and asthma with concurrent COPD. Data were weighted for the US population and analyses were stratified by age (< 40 and ≥ 40 years old).

Results

Of the 18,619 adults included, 1059 (5.6% [95% CI 5.1-5.9]) had current asthma. A substantial overlap was observed both in subjects aged < 40 years (44%) and ≥ 40 years (54%). The more prevalent specific overlaps in both age groups were AwObesity associated with either B-Eos-high (15 and 12%, respectively) or B-Eos&FeNO-low asthma (13 and 11%, respectively). About 14% of the current asthma patients were "non-classified". Regardless of phenotype classification, having concomitant phenotypes was significantly associated with (adjusted OR, 95% CI) ≥ 2 controller medications (2.03, 1.16-3.57), and FEV₁ < LLN (3.21, 1.74-5.94), adjusted for confounding variables.

Conclusions

A prevalent overlap of commonly reported asthma phenotypes was observed among asthma patients from the general population, with implications for objective asthma outcomes. A broader approach may be required to better characterize asthma patients and prevent poor asthma outcomes.

Potential of serum soluble CD93 as a biomarker for asthma in an ovalbumin-induced asthma murine model

BACKGROUND

CD93 is a membrane-associated glycoprotein, which can be released in a soluble form (sCD93) into the serum. CD93 has received renewed attention as a candidate biomarker of inflammation in various inflammatory and immune-mediated diseases, including asthma.

OBJECTIVE

We aimed to evaluate the effects of airway inflammation on CD93 levels in murine models.

METHODS

We established an ovalbumin (OVA)-induced acute asthma murine model (OVA model) and a lipopolysaccharide (LPS)-induced airway inflammation murine model (LPS model). Dexamethasone was administered by gavage to attenuate the airway inflammation.

RESULTS

The OVA model demonstrated typical allergic asthma features with increased airway hyper-responsiveness, inflammatory cell infiltration, increased Th2 cytokine levels, compared to the control group. CD93 levels were decreased in lung homogenates and, respiratory epithelial cells, whereas serum sCD93 levels were increased in the OVA model, as compared to the control group. Dexamethasone reversed these effects of OVA. In contrast, in the LPS model, CD93 levels were not affected in neither respiratory epithelial cells nor serum.

CONCLUSIONS

Our findings demonstrate the potential of using sCD93 as a biomarker for allergic asthma.

Blood biomarkers in chronic airways diseases and their role in diagnosis and management

INTRODUCTION

The complexity and heterogeneous nature of asthma and chronic obstructive pulmonary disease (COPD) results in difficulties in diagnosing and treating patients. Biomarkers that can identify underlying mechanisms, identify patient phenotypes and to predict treatment response could be of great value for adequate treatment. Areas covered: Biomarkers play an important role for the development of novel targeted therapies in airways disease. Blood biomarkers are relatively non-invasive, easy to obtain and easy to apply in routine care. Several blood biomarkers are being used to diagnose and monitor chronic airways diseases, as well as to predict response to treatment and long-term prognosis. Blood eosinophils are the best studied biomarker, the most applied in clinical practice, and until now the most promising of all blood biomarkers. Other blood biomarkers, including serum periostin, IgE and ECP and plasma fibrinogen are less studied and less relevant in clinical practice. Recent developments include the use of antibody assays of many different cytokines at the same time, and 'omics' techniques and systems medicine. Expert commentary: With the exception of blood eosinophils, the use of blood biomarkers in asthma and COPD has been rather disappointing. Future research using new technologies like big-data analysis of blood samples from real-life patient cohorts will probably gain better insight into underlying mechanisms of different disease phenotypes. Identification of specific molecular pathways and associated biomarkers will then allow the development of new targets for precision medicine.

Mucus plugs in patients with asthma linked to eosinophilia and airflow obstruction

BACKGROUND

The link between mucus plugs and airflow obstruction has not been established in chronic severe asthma, and the role of eosinophils and their products in mucus plug formation is unknown.

METHODS

In clinical studies, we developed and applied a bronchopulmonary segment-based scoring system to quantify mucus plugs on multidetector computed tomography (MDCT) lung scans from 146 subjects with asthma and 22 controls, and analyzed relationships among mucus plug scores, forced expiratory volume in 1 second (FEV1), and airway eosinophils. Additionally, we used airway mucus gel models to explore whether oxidants generated by eosinophil peroxidase (EPO) oxidize cysteine thiol groups to promote mucus plug formation.

RESULTS

Mucus plugs occurred in at least 1 of 20 lung segments in 58% of subjects with asthma and in only 4.5% of controls, and the plugs in subjects with asthma persisted in the same segment for years. A high mucus score (plugs in ≥ 4 segments) occurred in 67% of subjects with asthma with FEV1 of less than 60% of predicted volume, 19% with FEV1 of 60%-80%, and 6% with FEV1 greater than 80% (P < 0.001) and was associated with marked increases in sputum eosinophils and EPO. EPO catalyzed oxidation of thiocyanate and bromide by H2O2 to generate oxidants that crosslink cysteine thiol groups and stiffen thiolated hydrogels.

CONCLUSION

Mucus plugs are a plausible mechanism of chronic airflow obstruction in severe asthma, and EPO-generated oxidants may mediate mucus plug formation. We propose an approach for quantifying airway mucus plugging using MDCT lung scans and suggest that treating mucus plugs may improve airflow in chronic severe asthma.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01718197, NCT01606826, NCT01750411, NCT01761058, NCT01761630, NCT01759186, NCT01716494, and NCT01760915.

FUNDING

NIH grants P01 HL107201, R01 HL080414, U10 HL109146, U10 HL109164, U10 HL109172, U10 HL109086, U10 HL109250, U10 HL109168, U10 HL109257, U10 HL109152, and P01 HL107202 and National Center for Advancing Translational Sciences grants UL1TR0000427, UL1TR000448, and KL2TR000428.

Severe Asthma Phenotypes - How Should They Guide Evaluation and Treatment?

Although patients with "severe" asthma tend to be characterized by ongoing symptoms and airway inflammation despite treatment with high doses of inhaled and systemic corticosteroids, there is increasing recognition of marked phenotypic heterogeneity within affected patients. Although "precision medicine" approaches for patients with severe asthma are needed, there are many hurdles that must be overcome in daily practice. The National Heart, Lung and Blood Institute's Severe Asthma Research Program (SARP) has been at the forefront of phenotype discovery in severe asthma for the past decade. SARP, along with other international groups, has described clinical severe asthma phenotypes in both adults and children that can be evaluated in the clinical setting. Although these clinical phenotypes provide a good "starting point" for addressing disease heterogeneity in severe asthma in everyday practice, more efforts are needed to understand how these phenotypes relate to underlying disease mechanisms and pharmacological treatment responses. This review highlights the clinical asthma phenotypes identified to date, their associations with underlying endotypes and potential biomarkers, and remaining knowledge gaps that must be addressed before precision medicine can become a reality for patients with severe asthma.

Clinical and inflammatory phenotyping by breathomics in chronic airway diseases irrespective of the diagnostic label

Asthma and chronic obstructive pulmonary disease (COPD) are complex and overlapping diseases that include inflammatory phenotypes. Novel anti-eosinophilic/anti-neutrophilic strategies demand rapid inflammatory phenotyping, which might be accessible from exhaled breath.Our objective was to capture clinical/inflammatory phenotypes in patients with chronic airway disease using an electronic nose (eNose) in a training and validation set.This was a multicentre cross-sectional study in which exhaled breath from asthma and COPD patients (n=435; training n=321 and validation n=114) was analysed using eNose technology. Data analysis involved signal processing and statistics based on principal component analysis followed by unsupervised cluster analysis and supervised linear regression.Clustering based on eNose resulted in five significant combined asthma and COPD clusters that differed regarding ethnicity (p=0.01), systemic eosinophilia (p=0.02) and neutrophilia (p=0.03), body mass index (p=0.04), exhaled nitric oxide fraction (p<0.01), atopy (p<0.01) and exacerbation rate (p<0.01). Significant regression models were found for the prediction of eosinophilic (R²=0.581) and neutrophilic (R²=0.409) blood counts based on eNose. Similar clusters and regression results were obtained in the validation set.Phenotyping a combined sample of asthma and COPD patients using eNose provides validated clusters that are not determined by diagnosis, but rather by clinical/inflammatory characteristics. eNose identified systemic neutrophilia and/or eosinophilia in a dose-dependent manner.

Comparative Study of IL-33 and IL-6 Levels in Different Respiratory Samples in Mild-to-Moderate Asthma and COPD

IL-6 and IL-33 are involved in the inflammatory process in obstructive lung diseases. In contrast to IL-6, few data on the expression of IL-33 in different biological samples from asthma and COPD patients are available. The aim was to evaluate the expressions of IL-33 and IL-6 in bronchial mucosa and to compare these expressions with the concentrations of both cytokines in various respiratory samples from patients with mild-to-moderate asthma and COPD. Serum, induced sputum and exhaled breath condensate IL-6 and IL-33 levels, as well as their expression in bronchial mucosa were evaluated in 22 asthma and 33 COPD patients. There were significant differences between bronchial mucosa IL-6, but not IL-33 expression in asthma and COPD. Serum and IS IL-6 concentrations were higher in COPD than in asthma (3.4 vs. 2.02 pg/mL, p = 0.002 and 16.5 vs. 12.7 pg/mL, p = 0.007, respectively); IL-33 levels reached similar values in asthma and COPD in all investigated samples. In both diseases, the lowest levels of IL-6 and IL-33 were found in EBC. EBC levels of both cytokines did not correlate with their expression in other materials. The IL-33 and IL-6 are detectable in serum, IS and EBC not only in asthma but also in COPD patients. In the COPD group, serum and IS IL-6 concentrations were statistically higher than in the asthma group. The tissue expression of IL-33 and IL-33 concentrations in the investigated biological samples were on a comparable level in both diseases. Our findings may suggest that IL-33 activation is a common pathway in asthma and COPD.

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

BACKGROUND

Asthma and COPD are complex, heterogeneous conditions comprising a wide range of phenotypes, some of which are refractory to currently available treatments. Elucidation of these phenotypes and identification of biomarkers with which to recognize them and guide appropriate treatment remain a priority.

OBJECTIVE

This review describes the utility of blood eosinophils as a surrogate biomarker of eosinophilic airway inflammation, a common feature of specific asthma and COPD phenotypes. The role of blood eosinophils in airway disease is described, as is their relevance in reflecting airway eosinophilia. Each disease is discussed separately as the manner in which blood eosinophils might be used as biomarkers differs. Focusing on patients with severe disease (persistent eosinophilic asthma and exacerbating COPD), we evaluate evidence examining eosinophils as biomarkers.

RESULTS

In asthma, the rationale for using blood eosinophils to guide treatment is clearly defined, backed by prospective, well-controlled studies. Higher eosinophil counts identify patients with more severe disease and poorer outcomes, patients for whom biologic therapies targeting allergic and/or eosinophilic pathways are recommended. In COPD, the evidence is less robust. High blood eosinophil counts are a modest predictor of future exacerbations, and may predict a favourable response to ICS on top of LABA/LAMA, especially in patients with a history of frequent exacerbations.

CONCLUSION

Before extensive application in clinical practice, further evaluation of these findings in prospective clinical studies, and standardization of the appropriate thresholds of clinically relevant eosinophilia are needed, together with establishing whether single or multiple measurements are required in different clinical settings.

Assessment of eosinophilic airway inflammation as a contribution to the diagnosis of occupational asthma

BACKGROUND

Ascertaining the presence of asthma through the assessment of nonspecific bronchial hyperresponsiveness (NSBH) is a key step in the diagnosis of occupational asthma (OA). We aimed at investigating whether indices of airway inflammation including fractional exhaled nitric oxide (FeNO) and sputum eosinophils would be useful adjuncts to the measurement of NSBH in diagnosing OA defined as a positive specific inhalation challenge (SIC).

METHODS

The study included 240 consecutive subjects with a suspicion of OA who completed a SIC, of whom 133 showed a positive response. The sensitivity, specificity, and predictive values of NSBH, and FeNO, as well as sputum eosinophil counts assessed at baseline of the SIC were determined.

RESULTS

A concentration of histamine inducing a 20% decline in FEV₁ (PC₂₀ ) ≤16 mg/mL showed a sensitivity of 87% and a specificity of 36%. A FeNO level ≥25 ppb and a sputum eosinophil count ≥2% provided lower sensitivity rates (47% and 39%, respectively) than the PC₂₀ value. Eight of the 17 subjects without baseline NSBH despite a positive SIC showed a sputum eosinophil count ≥2%, a FeNO level ≥25 ppb, or both outcomes. Combining either a PC₂₀ value ≤16 mg/mL or a FeNO ≥25 ppb increased the sensitivity to 91%. Using either a PC₂₀ ≤16 mg/mL or a sputum eosinophil count ≥1% increased the sensitivity to 94%.

CONCLUSION

Adding the assessment of FeNO level and sputum eosinophils to NSBH improves the identification of subjects who may have OA and require further objective testing before excluding the possibility of OA.

A Pathogenic Relationship of Bronchopulmonary Dysplasia and Retinopathy of Prematurity? A Review of Angiogenic Mediators in Both Diseases

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are common and significant morbidities of prematurely born infants. These diseases have in common altered and pathologic vascular formation in the face of incomplete organ development. Therefore, it is reasonable to question whether factors affecting angiogenesis could have a joint pathogenic role for both diseases. Inhibition or induced expression of a single angiogenic factor is unlikely to be 100% causative or protective of either of BPD or ROP. It is more likely that interactions of multiple factors leading to disordered angiogenesis are present, increasing the likelihood of common pathways in both diseases. This review explores this possibility by assessing the evidence showing involvement of specific angiogenic factors in the vascular development and maldevelopment in each disease. Theoretical interactions of specific factors mutually contributing to BPD and ROP are proposed and, where possible, a timeline of the proposed relationships between BPD and ROP is developed. It is hoped that future research will be inspired by the theories put forth in this review to enhance the understanding of the pathogenesis in both diseases.

Sputum cell IL-1 receptor expression level is a marker of airway neutrophilia and airflow obstruction in asthmatic patients

BACKGROUND

Various clinical, biologic, or physiologic markers of asthma have been used to identify patient clusters and potential targets for therapy. However, these identifiers frequently overlap among the different asthma groups. For instance, both eosinophil and neutrophil counts are often increased in the airways of asthmatic patients despite their typical association with type 2 and type 17 immune response, respectively.

OBJECTIVES

We sought to determine whether inflammatory gene expression is related to patterns of airway inflammation and lung function and identify molecular markers for neutrophilic asthma.

METHODS

Expression levels of 17 genes characterizing type 1, type 2, and type 17 lymphocytes were measured in sputum samples from 48 participants with asthma. The relationships between gene expression levels and sputum cell differentials or measures of pulmonary function were examined by using partial least squares regression.

RESULTS

Gene expression levels were strongly associated with cell differentials, explaining 71% of variation in eosinophil counts and 64% of variation in neutrophil counts. The 3 genes with the strongest relationships to sputum neutrophil counts were IL1R1 (standardized regression coefficient [β] = +0.27, P = .005), IL1RAP (β = +0.32, P = .0004), and IL4R (β = +0.29, P = .002). Higher expression levels of IL1R1, IL1RAP, and IL4R were associated with reduced FEV₁/forced vital capacity ratio (β = -0.11, -0.08, and -0.10; P = .005, .07, and .05).

CONCLUSION

IL-1 receptor appears to be a marker of neutrophilic inflammation and airflow obstruction in patients with asthma, who have a wide range of disease severity. The IL-1 pathway might contribute to airway neutrophilia and is a potential therapeutic target in patients with neutrophilic asthma.

Biomarkers for severe eosinophilic asthma

The last decade has seen the approval of several new biologics for the treatment of severe asthma-targeting specific endotypes and phenotypes. This review will examine how evidence generated from the mepolizumab clinical development program showed that blood eosinophil counts, rather than sputum or tissue eosinophil counts, evolved as a pharmacodynamic and predictive biomarker for the efficacy of treatment with mepolizumab in patients with severe eosinophilic asthma. Based on the available evidence and combined with clinical judgement, a baseline blood eosinophil threshold of 150 cells/μL or greater or a historical blood eosinophil threshold of 300 cells/μL or greater will allow selection of patients with severe eosinophilic asthma who are most likely to achieve clinically significant reductions in the rate of exacerbations with mepolizumab treatment.

Revisiting Type 2-high and Type 2-low airway inflammation in asthma: current knowledge and therapeutic implications

Asthma is a complex respiratory disorder characterized by marked heterogeneity in individual patient disease triggers and response to therapy. Several asthma phenotypes have now been identified, each defined by a unique interaction between genetic and environmental factors, including inflammatory, clinical and trigger-related phenotypes. Endotypes further describe the functional or pathophysiologic mechanisms underlying the patient's disease. type 2-driven asthma is an emerging nomenclature for a common subtype of asthma and is characterized by the release of signature cytokines IL-4, IL-5 and IL-13 from cells of both the innate and adaptive immune systems. A number of well-recognized biomarkers have been linked to mechanisms involved in type 2 airway inflammation, including fractional exhaled nitric oxide, serum IgE, periostin, and blood and sputum eosinophils. These type 2 cytokines are targets for pharmaceutical intervention, and a number of therapeutic options are under clinical investigation for the management of patients with uncontrolled severe asthma. Anticipating and understanding the heterogeneity of asthma and subsequent improved characterization of different phenotypes and endotypes must guide the selection of treatment to meet individual patients' needs.

Eosinophilic Endotype of Asthma

Asthma is a heterogeneous disease that can be classified into different clinical endotypes, depending on the type of airway inflammation, clinical severity, and response to treatment. This article focuses on the eosinophilic endotype of asthma, which is defined by the central role that eosinophils play in the pathophysiology of the condition. It is characterized by elevated sputum and/or blood eosinophils on at least 2 occasions and by a significant response to treatments that suppress eosinophilia. Histopathologic demonstration of eosinophils in the airways provides the most direct diagnosis of eosinophilic asthma; but it is invasive, thus, impractical in clinical practice.

Biomarkers in Severe Asthma

Biomarkers have been critical for studies of disease pathogenesis and the development of new therapies in severe asthma. In particular, biomarkers of type 2 inflammation have proven valuable for endotyping and targeting new biological agents. Because of these successes in understanding and marking type 2 inflammation, lack of knowledge regarding non-type 2 inflammatory mechanisms in asthma will soon be the major obstacle to the development of new treatments and management strategies in severe asthma. Biomarkers can play a role in these investigations as well by providing insight into the underlying biology in human studies of patients with severe asthma.

Relationship between sputum clusterin levels and childhood asthma

BACKGROUND

Clusterin is a sensitive cellular biosensor of oxidative stress and has been studied as a biomarker for inflammation-associated diseases. Clusterin levels in childhood asthma have not been evaluated.

OBJECTIVES

(1) To evaluate sputum clusterin levels in children with asthma compared to a control group. (2) To assess the relationships between sputum clusterin levels and airway inflammation, pulmonary function, and bronchial hyperresponsiveness.

METHODS

This study included 170 children aged 5-18 years with stable asthma (n = 91), asthma exacerbation (n = 29), or no asthma (healthy controls; n = 50). Induced sputum, pulmonary function, and methacholine challenge tests were performed. Stable asthma was classified into two groups according to the severity. Clusterin levels in sputum were measured using an enzyme-linked immunosorbent assay.

RESULTS

Children with stable asthma had a higher clusterin level than healthy controls [4540 (3872-5651) pg/mL vs. 3857 (1054-4369) pg/mL, P < 0.001]. The clusterin level was also more elevated in eosinophil-dominant sputum than in non-eosinophilic sputum in stable asthma [5094 (4243-6257) pg/mL vs. 4110 (1871-4839) pg/mL, P = 0.0017]. Clusterin levels were associated with asthma severity. Paradoxically, clusterin levels were lower during asthma exacerbation than in stable asthma [1838 (350-4790] pg/mL vs. 4540 (3872-5651) pg/mL, P < 0.001]. Clusterin levels were strongly correlated with the methacholine concentration that caused a 20% decrease in the forced expiratory volume in 1 s (r = -0.617, P < 0.001); there was no significant correlation between clusterin levels and other pulmonary function parameters.

CONCLUSIONS AND CLINICAL RELEVANCE

Clusterin levels were altered in children with stable asthma and asthma exacerbation because of its antioxidant and anti-inflammatory effects. Clusterin may be a marker that reflects airway inflammation and severity of symptoms, and it can be used in the assessment and management of childhood asthma.

Menopausal asthma-much ado about nothing? An observational study

OBJECTIVE

Menopausal asthma is considered a distinct asthma phenotype. Our aim was to identify potential specific features of asthma in postmenopausal women in a cohort of Polish females.

METHODS

Asthma severity and control, pulmonary function, exhaled nitric oxide (FE_NO), peripheral blood and induced sputum (IS) differential cell count were compared in three groups: women with premenopausal asthma (group 1), menopausal women with pre-existing asthma (group 2A) and menopausal women with asthma onset in the perimenopausal or menopausal period (group 2B).

RESULTS

We enrolled 27 women to group 1, 13 to group 2A and 16 to group 2B. Asthma severity and control, blood eosinophil count and FE_NO did not differ among the groups. Menopausal women had a higher incidence of irreversible airway obstruction (84.6% in group 2A and 56.2% in group 2B vs. 22.2% in group 1, p < 0.001 and p = 0.03, respectively). The proportion of patients with sputum eosinophilia was highest in menopausal women with pre-existing asthma, although the difference did not reach statistical significance (88.9% in group 2A vs. 66.7% in group 2B and 65.0% in group 1, respectively, p = 0.86).

CONCLUSIONS

Menopausal women with asthma are characterized by an increased incidence of irreversible airway obstruction regardless of disease duration. This may indicate that age may contribute to pulmonary function impairment in asthmatic women independently of their hormonal status at the time of asthma diagnosis. Our results failed to confirm the presence of specific asthma features which would allow to distinguish the phenotype of menopausal asthma.

Association of sputum and blood eosinophil concentrations with clinical measures of COPD severity: an analysis of the SPIROMICS cohort

BACKGROUND

Increased concentrations of eosinophils in blood and sputum in chronic obstructive pulmonary disease (COPD) have been associated with increased frequency of exacerbations, reduced lung function, and corticosteroid responsiveness. We aimed to assess whether high eosinophil concentrations in either sputum or blood are associated with a severe COPD phenotype, including greater exacerbation frequency, and whether blood eosinophils are predictive of sputum eosinophils.

METHODS

We did a multicentre observational study analysing comprehensive baseline data from SPIROMICS in patients with COPD aged 40-80 years who had a smoking history of at least 20 pack-years, recruited from six clinical sites and additional subsites in the USA between Nov 12, 2010, and April 21, 2015. Inclusion criteria for this analysis were SPIROMICS baseline visit data with complete blood cell counts and, in a subset, acceptable sputum counts. We stratified patients on the basis of blood and sputum eosinophil concentrations and compared their demographic characteristics, as well as results from questionnaires, clinical assessments, and quantitative CT (QCT). We also analysed whether blood eosinophil concentrations reliably predicted sputum eosinophil concentrations. This study is registered with ClinicalTrials.gov (NCT01969344).

FINDINGS

Of the 2737 patients recruited to SPIROMICS, 2499 patients were smokers and had available blood counts, and so were stratified by mean blood eosinophil count: 1262 patients with low (<200 cells per μL) and 1237 with high (≥200 cells per μL) blood eosinophil counts. 827 patients were eligible for stratification by mean sputum eosinophil percentage: 656 with low (<1·25%) and 171 with high (≥1·25%) sputum eosinophil percentages. The high sputum eosinophil group had significantly lower median FEV1 percentage predicted than the low sputum eosinophil group both before (65·7% [IQR 51·8-81·3] vs 75·7% [59·3-90·2], p<0·0001) and after (77·3% [63·1-88·5] vs 82·9% [67·8-95·9], p=0·001) bronchodilation. QCT density measures for emphysema and air trapping were significantly higher in the high sputum eosinophil group than the low sputum eosinophil group. Exacerbations requiring corticosteroids treatment were more common in the high versus low sputum eosinophil group (p=0·002). FEV1 percentage predicted was significantly different between low and high blood eosinophil groups, but differences were less than those observed between the sputum groups. The high blood eosinophil group had slightly increased airway wall thickness (0·02 mm difference, p=0·032), higher St George Respiratory Questionnaire symptom scores (p=0·037), and increased wheezing (p=0·018), but no evidence of an association with COPD exacerbations (p=0·35) or the other indices of COPD severity, such as emphysema measured by CT density, COPD assessment test scores, Body-mass index, airflow Obstruction, Dyspnea, and Exercise index, or Global Initiative for Chronic Obstructive Lung Disease stage. Blood eosinophil counts showed a weak but significant association with sputum eosinophil counts (receiver operating characteristic area under the curve of 0·64, p<0·0001), but with a high false-discovery rate of 72%.

INTERPRETATION

In a large, well characterised cohort of former and current smoking patients with a broad range of COPD severity, high concentrations of sputum eosinophils were a better biomarker than high concentrations of blood eosinophils to identify a patient subgroup with more severe disease, more frequent exacerbations, and increased emphysema by QCT. Blood eosinophils alone were not a reliable biomarker for COPD severity or exacerbations, or for sputum eosinophils. Clinical trials targeting eosinophilic inflammation in COPD should consider assessing sputum eosinophils.

FUNDING

National Institutes of Health, and National Heart, Lung, and Blood Institute.

Predictors of enhanced response with benralizumab for patients with severe asthma: pooled analysis of the SIROCCO and CALIMA studies

BACKGROUND

Benralizumab is an anti-eosinophilic, anti-interleukin-5 receptor α monoclonal antibody that has been shown to significantly reduce asthma exacerbations and improve lung function for patients with severe, uncontrolled asthma. We further explored the efficacy of benralizumab for patients with different baseline blood eosinophil thresholds and exacerbation histories.

METHODS

This study is a pooled analysis of the results from the randomised, double-blind, placebo-controlled SIROCCO (NCT01928771) and CALIMA (NCT01914757) phase 3 studies. In these studies, patients with severe, uncontrolled asthma were randomly assigned (1:1:1) to receive subcutaneous benralizumab 30 mg, either every 4 weeks or every 8 weeks (with first three doses given every 4 weeks), or placebo every 4 weeks. The primary endpoint was annual exacerbation rate (AER) ratio versus placebo, analysed by baseline eosinophil counts (≥0, ≥150, ≥300, or ≥450 cells per μL) and by number of exacerbations (two vs three or more) during the year before enrolment. The analyses were done in accordance with the intention-to-treat principle.

FINDINGS

Of 2295 patients, 756 received benralizumab every 4 weeks, 762 received benralizumab every 8 weeks, and 777 patients received placebo. AER among patients with baseline blood eosinophil counts of at least 0 cells per μL was 1·16 (95% CI 1·05-1·28) in patients who received placebo versus 0·75 (0·66-0·84) in patients who received benralizumab every 8 weeks (rate ratio 0·64, 0·55-0·75; p<0·0001). In patients who received benralizumab every 4 weeks who had eosinophil counts of 0 or more cells per μL, AER was 0·73 (0·65-0·82); rate ratio versus placebo was 0·63 (0·54-0·74; p<0·0001). The extent to which exacerbation rates were reduced increased with increasing blood eosinophil thresholds and with greater exacerbation history in patients in the 4-weekly and 8-weekly benralizumab groups. Greater improvements in AER were seen with benralizumab compared with placebo for patients with a combination of high blood eosinophil thresholds and a history of more frequent exacerbations.

INTERPRETATION

These results will help to guide clinicians when they are deciding whether to use benralizumab to treat patients with severe, uncontrolled, eosinophilic asthma.

FUNDING

AstraZeneca.

The association between blood eosinophil count and benralizumab efficacy for patients with severe, uncontrolled asthma: subanalyses of the Phase III SIROCCO and CALIMA studies

OBJECTIVE

Benralizumab, an anti-eosinophilic monoclonal antibody, in combination with high-dosage inhaled corticosteroids and long-acting β₂-agonists (ICS/LABA), significantly reduced asthma exacerbations, improved lung function, and reduced symptoms for patients with severe, uncontrolled asthma with blood eosinophil counts ≥300 cells/μL in the Phase III SIROCCO and CALIMA studies. To understand the efficacy and safety of benralizumab for patients with eosinophil-driven disease with blood eosinophil counts lower than 300 cells/μL, we evaluated the effect of applying an eosinophil cutoff of ≥150 cells/μL.

METHODS

Adult patients with uncontrolled asthma despite high-dosage ICS/LABA ± additional asthma controller(s) received subcutaneous benralizumab 30 mg every 8 weeks (Q8W; first three doses every 4 weeks) or placebo for 48 (SIROCCO) or 56 (CALIMA) weeks. Efficacy measures including annual exacerbation rate, prebronchodilator FEV₁, and total asthma symptom score were analyzed by baseline blood eosinophil counts ≥150 vs. <150 cells/μL.

RESULTS

Benralizumab reduced asthma exacerbation rates by 42% in SIROCCO (rate ratio = 0.58; 95% CI = 0.46-0.74; p < 0.001; n = 325) and 36% in CALIMA (rate ratio = 0.64; 95% CI = 0.50-0.81; p < 0.001; n = 300) vs. placebo (n = 306 for SIROCCO, n = 315 for CALIMA) for patients with blood eosinophil counts ≥150 cells/μL. Benralizumab increased prebronchodilator FEV₁ (both studies, p ≤ 0.002) and improved total asthma symptom score in SIROCCO (p = 0.009) at end of treatment vs. placebo for patients with blood eosinophil counts ≥150 cells/μL. The overall adverse events frequency was similar between treatment groups and eosinophil count cohorts.

CONCLUSION

These results support the efficacy and safety of benralizumab for patients with severe asthma and blood eosinophil counts ≥150 cells/μL.

Clinical and biological characteristics of the French COBRA cohort of adult subjects with asthma

The COhort of BRonchial obstruction and Asthma (COBRA) is a longitudinal cohort that involves 12 French academic institutions. DNA, serum samples and clinical data are collected at entry and every 6 months thereafter.Of 1080 patients with asthma recruited between 2007 and 2015, 401 had mild/moderate and 613 had severe asthma. In cross-sectional analyses, compared with patients with milder disease, patients with severe asthma had more symptoms, exacerbations, hospitalisations and visits to the emergency department during the preceding 12 months, higher numbers of blood eosinophils, and more comorbidities. More than 60% of patients with severe asthma were therapy-uncontrolled at entry, and 152 of them were being treated with omalizumab. In addition, patients with asthma who had the highest eosinophilia levels (>300/mm³) had shorter asthma duration, lower lung function, and higher rates of severe exacerbations and unacceptable asthma control than patients with lower eosinophil counts.Longitudinal analyses performed in 427 patients with asthma with at least three differential blood cell counts demonstrated that both eosinophil numbers and eosinophil increase over time were associated with the number of exacerbations occurring until the next visit and with Juniper score.Studies with the COBRA cohort will help to improve knowledge concerning the risk and biological factors associated with asthma severity and to better understand their influence on the disease trajectory.

Phenotype-Driven Therapeutics in Severe Asthma

Inhaled corticosteroids are the mainstay of asthma treatment using a step-up approach with incremental dosing and additional controller medications in order to achieve symptom control and prevent exacerbations. While most patients respond well to this treatment approach, some patients remain refractory despite high doses of inhaled corticosteroids and a long-acting β-agonist. The problem lies in the heterogeneity of severe asthma, which is further supported by the emergence of severe asthma phenotypes. This heterogeneity contributes to the variability in treatment response. Randomized controlled trials involving add-on therapies in poorly controlled asthma have challenged the idea of a "one size fits all" approach targeting specific phenotypes in their subject selection. This review discusses severe asthma phenotypes from unbiased clustering approaches and the most recent scientific evidence on novel treatments to provide a guide in personalizing severe asthma treatment.

Is it possible to claim or refute sputum eosinophils ≥ 3% in asthmatics with sufficient accuracy using biomarkers?

The concept of asthma inflammatory phenotypes has proved to be important in predicting response to inhaled corticosteroids. Induced sputum, which has been pivotal in the development of the concept of inflammatory phenotypes, is however not widely available. Several studies have proposed to use surrogate exhaled or blood biomarkers, like fractional exhaled nitric oxide (FENO), blood eosinophils and total serum immunoglobulin E (IgE). However, taken alone, each of these biomarkers has moderate accuracy to identify sputum eosinophilia. Here, we propose a new approach based on the likelihood ratio to study which thresholds of these biomarkers, taken alone or in combination, were able to rule in or rule out sputum eosinophils ≥3%. We showed in a large population of 869 asthmatics that combining FENO, blood eosinophils and total serum IgE could accurately predict sputum eosinophils ≥ or <3% in 58% of our population.

Management of Severe Asthma before Referral to the Severe Asthma Specialist

Severe asthma is associated with significant morbidity and can be challenging to assess and control, due to heterogeneity of disease, complexity of diagnosis, and impact of comorbidities. A structured approach to the assessment and management of severe asthma may be helpful to the practicing clinician. First, it is important to confirm a diagnosis of asthma. In patients who are either not responding to treatment, or who require high doses of medication to control symptoms, it is highly possible that disease mimickers or comorbidities are present and can inhibit therapeutic responsiveness. The assessment and management of common comorbidities of asthma may dramatically impact disease control and thus medication requirement. Determining medication adherence and optimizing drug dose and delivery may separate out truly severe asthmatics from those not using medications regularly or properly. Next, although true personalized medicine for severe asthma is not yet realized, for those individuals with severe asthma, phenotypic characteristics of each patient may guide which therapeutic options may be most effective for that patient. Finally, evaluation and management of severe asthma at a referral center can add additional phenotyping, therapeutic, and diagnostic strategies.