Phenotypes determined by cluster analysis in severe or difficult-to-treat asthma

The Impact of High-Fructose Diet and Co-Sensitization to House Dust Mites and Ragweed Pollen on the Modulation of Airway Reactivity and Serum Biomarkers in Rats

The topic of ragweed pollen (RW) versus house dust mites (HDMs) has often been deliberated, but the increasing incidence of co-sensitization between them has been scarcely addressed. Utilizing Sprague Dawley rats, we explored the effects of co-sensitization with the combination of HDMs and RW pollen extracts in correlation with high-fructose diet (HFrD) by in vitro tracheal reactivity analysis in isolated organ bath and biological explorations. Our findings unveiled interrelated connections between allergic asthma, dyslipidemia, and HFrD-induced obesity, shedding light on their compounding role through inflammation. The increased CRP values and airway hyperresponsiveness to the methacholine challenge suggest a synergistic effect of obesity on amplifying the existing inflammation induced by asthma. One of the major outcomes is that the co-sensitization to HDMs and RW pollen led to the development of a severe allergic asthma phenotype in rats, especially in those with HFrD. Therefore, the co-sensitization to these allergens as well as the HFrD may play a crucial role in the modulation of systemic inflammation, obesity, and airway reactivity.

Novel Machine Learning Identifies 5 Asthma Phenotypes Using Cluster Analysis of Real-World Data

BACKGROUND

Asthma classification into different subphenotypes is important to guide personalized therapy and improve outcomes.

OBJECTIVES

To further explore asthma heterogeneity through determination of multiple patient groups by using novel machine learning (ML) approaches and large-scale real-world data.

METHODS

We used electronic health records of patients with asthma followed at the Cleveland Clinic between 2010 and 2021. We used k-prototype unsupervised ML to develop a clustering model where predictors were age, sex, race, body mass index, prebronchodilator and postbronchodilator spirometry measurements, and the usage of inhaled/systemic steroids. We applied elbow and silhouette plots to select the optimal number of clusters. These clusters were then evaluated through LightGBM's supervised ML approach on their cross-validated F1 score to support their distinctiveness.

RESULTS

Data from 13,498 patients with asthma with available postbronchodilator spirometry measurements were extracted to identify 5 stable clusters. Cluster 1 included a young nonsevere asthma population with normal lung function and higher frequency of acute exacerbation (0.8 /patient-year). Cluster 2 had the highest body mass index (mean ± SD, 44.44 ± 7.83 kg/m2), and the highest proportion of females (77.5%) and Blacks (28.9%). Cluster 3 comprised patients with normal lung function. Cluster 4 included patients with lower percent of predicted FEV1 of 77.03 (12.79) and poor response to bronchodilators. Cluster 5 had the lowest percent of predicted FEV1 of 68.08 (15.02), the highest postbronchodilator reversibility, and the highest proportion of severe asthma (44.9%) and blood eosinophilia (>300 cells/μL) (34.8%).

CONCLUSIONS

Using real-world data and unsupervised ML, we classified asthma into 5 clinically important subphenotypes where group-specific asthma treatment and management strategies can be designed and deployed.

Clinical Characteristics and Outcomes of the Phenotypes of COPD-Bronchiectasis Association

INTRODUCTION

Although COPD may frequently co-exist with bronchiectasis [COPD-bronchiectasis associated (CBA)], little is known regarding the clinical heterogeneity. We aimed to identify the phenotypes and compare the clinical characteristics and prognosis of CBA.

METHODS

We conducted a retrospective cohort study involving 2928 bronchiectasis patients, 5158 COPD patients, and 1219 patients with CBA hospitalized between July 2017 and December 2020. We phenotyped CBA with a two-step clustering approach and validated in an independent retrospective cohort with decision-tree algorithms.

RESULTS

Compared with patients with COPD or bronchiectasis alone, patients with CBA had significantly longer disease duration, greater lung function impairment, and increased use of intravenous antibiotics during hospitalization. We identified five clusters of CBA. Cluster 1 (N=120, CBA-MS) had predominantly moderate-severe bronchiectasis, Cluster 2 (N=108, CBA-FH) was characterized by frequent hospitalization within the previous year, Cluster 3 (N=163, CBA-BI) had bacterial infection, Cluster 4 (N=143, CBA-NB) had infrequent hospitalization but no bacterial infection, and Cluster 5 (N=113, CBA-NHB) had no hospitalization or bacterial infection in the past year. The decision-tree model predicted the cluster assignment in the validation cohort with 91.8% accuracy. CBA-MS, CBA-BI, and CBA-FH exhibited higher risks of hospital re-admission and intensive care unit admission compared with CBA-NHB during follow-up (all P<0.05). Of the five clusters, CBA-FH conferred the worst clinical prognosis.

CONCLUSION

Bronchiectasis severity, recent hospitalizations and sputum culture findings are three defining variables accounting for most heterogeneity of CBA, the characterization of which will help refine personalized clinical management.

Pre-asthma: a useful concept? A EUFOREA paper. Part 2-late onset eosinophilic asthma

The concept of pre-diabetes has led to provision of measures to reduce disease progression through identification of subjects at risk of diabetes. We previously considered the idea of pre-asthma in relation to allergic asthma and considered that, in addition to the need to improve population health via multiple measures, including reduction of exposure to allergens and pollutants and avoidance of obesity, there are several possible specific means to reduce asthma development in those most at risk (pre- asthma). The most obvious is allergen immunotherapy (AIT), which when given for allergic rhinitis (AR) has reasonable evidence to support asthma prevention in children (2) but also needs further study as primary prevention. In this second paper we explore the possibilities for similar actions in late onset eosinophilic asthma.

Treatable Traits in Asthma: The Importance of Extrapulmonary Traits-GERD, CRSwNP, Atopic Dermatitis, and Depression/Anxiety

Treatable traits is a personalized medicine approach to the management of airway disease. Assessing traits within the 3 domains of pulmonary, extrapulmonary, and behavioral/lifestyle/risk factor traits, and applying targeted treatments to effectively manage these traits, enables a holistic and personalized approach to care. Asthma is a heterogeneous and complex airway disease that is frequently complicated by several extrapulmonary traits that impact asthma outcomes and predict future outcomes. We propose that the identification of extrapulmonary and behavioral risk factor traits and the implementation of targeted therapy will lead to improved management of people with asthma. Furthermore, many extrapulmonary traits present as "connected comorbidities"; that is, they coexist with asthma, have an impact on asthma, and effective treatment improves both asthma and the comorbidity or the comorbidities may share a similar mechanism. In this review, we explore this concept and look at atopic dermatitis, chronic rhinosinusitis with nasal polyps, gastroesophageal reflux disease, anxiety, and depression as treatable traits of asthma and how these can be managed using this approach.

Cluster analysis of phenotypes, job exposure, and inflammatory patterns in elderly and nonelderly asthma patients

BACKGROUND

Asthma has been identified as different phenotypes due to various risk factors. Age differences may have potential effects on asthma phenotypes. Our study aimed to identify potential asthma phenotypes among adults divided by age as either younger or older than 65 years. We also compared differences in blood granulocyte patterns, occupational asthmagens, and asthma control-related outcomes among patient phenotype clusters.

METHODS

We recruited nonelderly (<65 years old) (n = 726) and elderly adults (≥65 years old) (n = 201) with mild-to-severe asthma. We conducted a factor analysis to select 17 variables. A two-step cluster analysis was used to classify subjects with asthma phenotypes, and a discriminant analysis was used to verify the classification of cluster results.

RESULTS

There were three clusters with different characteristics identified in both the nonelderly and elderly asthmatic adults. In the nonelderly patient group, cluster 2 (obese, neutrophilic phenotypes) had a 1.85-fold significantly increased risk of asthma exacerbations. Cluster 3 (early-onset, atopy, and smoker with an eosinophil-predominant pattern) had a 2.37-fold risk of asthma exacerbations and higher oral corticosteroid (OCS) use than cluster 1 (late-onset and LMW exposure with paucigranulocytic blood pattern). Among elderly patients, cluster 2 had poor lung function and more ex-smokers. Cluster 3 (early-onset, long asthma duration) had the lowest paucigranulocytic blood pattern percentages in the elderly group.

CONCLUSIONS

The novelty of the clusters was found in age-dependent clusters. We identified three distinct phenotypes with heterogeneous characteristics, asthma exacerbations and medicine use in nonelderly and elderly asthmatic patients, respectively. Classification of age-stratified asthma phenotypes may lead to precise identification of patients, which provides personalized disease management.

What's new in pediatric asthma and rhinitis phenotypes and endotypes?

PURPOSE OF REVIEW

This review explores the evolving landscape of pediatric asthma and rhinitis, focusing on identifying and characterizing different subtypes.

RECENT FINDINGS

Childhood asthma and rhinitis are prevalent respiratory conditions frequently occurring together. To address the need for a precise definition of these diseases, an unbiased and comprehensive phenotyping approach has been undertaken with hypothesis-free analysis of extensive datasets to uncover new relationships among clinical, environmental, and biological characteristics. On the other hand, the concept of endotype is elaborate and multifaceted, representing distinct pathophysiological mechanisms underlying the clinical presentation and requires the identification of reliable biomarkers. The recognition of multiple inflammatory endotypes underscores the need for in-depth characterization, which could revolutionize the treatment landscape.

SUMMARY

Comprehending phenotypes and endotypes is crucial for customizing effective and personalized management approaches for children with asthma and rhinitis. More precise and efficient care can be administered through recognition and detailed characterization, ultimately enhancing patients' quality of life.

Clinical characteristics of obese, fixed airway obstruction, exacerbation-prone phenotype and comorbidities among severe asthma patients: a single-center study

BACKGROUND

Severe asthma places a large burden on patients and society. The characteristics of patients with severe asthma in the Chinese population remain unclear.

METHODS

A retrospective review was conducted in patients with severe asthma. Demographic and clinical data were collected. Patients were grouped according to phenotypes in terms of exacerbations, body mass index (BMI) and fixed airway obstruction (FAO) status, and the characteristics of different groups were compared. Comorbidities, factors that influence asthma phenotypes, were also analyzed in the study.

RESULTS

A total of 228 patients with severe asthma were included in our study. They were more likely to be overweight or obese. A total of 41.7% of the patients received GINA step 5 therapy, and 43.4% had a history of receiving regular or intermittent oral corticosteroids (OCS). Severe asthmatic patients with comorbidities were prone to have more asthma symptoms and decreased quality of life than patients without comorbidities. Patients with exacerbations were characterized by longer duration of asthma, poorer lung function, and worse asthma control. Overweight or obese patients tended to have more asthma symptoms, poorer lung function and more asthma-related comorbidities. Compared to patients without FAO, those in the FAO group were older, with longer duration of asthma and more exacerbations.

CONCLUSION

The existence of comorbidities in patients with severe asthma could result in more asthma symptoms and decreased quality of life. Patients with exacerbations or with overweight or obese phenotypes were characterized by poorer lung function and worse asthma control. Patients with FAO phenotype tended to have more exacerbations.

Obesity-related asthma and its relationship with microbiota

Obesity and asthma are global public health problems. Obesity-related asthma is a special phenotype of asthma with a complex pathogenesis. Its occurrence and development are related to mechanical compression, inflammatory response, metabolic regulation, gene regulation, and vitamin D deficiency. Different treatment strategies used in the process of weight loss have a beneficial impact on asthma. Alterations in gut and airway microbial community structure and their metabolites may also contribute to obesity-related asthma. The role of the Th17/Treg balance in the gut microbiota regulating the immune responses and host metabolism is important. Therapeutic measures associated with the gut microbiota variety may contribute to improving chronic inflammation associated with obesity by regulating the Th17/Treg balance. An early reduction in microbial diversity can predict the development of asthma and lead to allergy through an imbalance of Th2/Th1 responses. Short-chain fatty acids (SCFAs) regulate the differentiation and activation of regulatory T cells, thereby regulating immune homeostasis in the lung to suppress allergic inflammation and weight gain. Therefore, clarifying the microbial mechanism of obesity-related asthma has important guiding significance for clinical treatment. In this review, we used the following terms: "asthma and obesity" and "obesity-related asthma", combining "phenotype", "airway inflammation" and "lung function", and reviewed the characteristics and pathogenesis of obesity-related asthma, the relationship between the gut and airway microbiota and obesity-related asthma, and the current treatment measures for the disease.

Severity of adult-onset asthma - a matter of blood neutrophils and severe obesity

BACKGROUND

Adult-onset asthma is associated with a poor treatment response. The aim was to study associations between clinical characteristics, asthma control and treatment in adult-onset asthma.

METHODS

Previous participants within the population-based Obstructive Lung Disease in Northern Sweden studies (OLIN) were in 2019-2020 invited to clinical examinations including structured interviews, spirometry, fractional exhaled nitric oxide (FeNO), skin prick test and blood sampling. In total, n = 251 individuals with adult-onset asthma (debut >15 years of age) were identified. Uncontrolled asthma was defined according to ERS/ATS and treatment step according to GINA (2019).

RESULTS

Among individuals with uncontrolled asthma (34%), severe obesity (16.3% vs 7.9%, p = 0.041) and elevated levels of blood neutrophils, both regarding mean level of blood neutrophils (4.25*109/L vs 3.67*109/L, p = 0.003), and proportions with ≥4*109/L (49.4% vs 33.3%, p = 0.017) and ≥5*109/L (32.1% vs 13.7%, p < 0.001) were more common than among those with controlled asthma. Adding the dimension of GINA treatment step 1-5, individuals with uncontrolled asthma on step 4-5 treatment had the highest proportions of blood neutrophils ≥5*109/L (45.5%), severe obesity (BMI≥35, 26.1%), dyspnea (mMRC≥2) (34.8%), and most impaired lung function in terms of FEV1%<80% of predicted (42.9%), FEV1

CONCLUSION

This study indicates that in adult-onset asthma, primarily non-type-2 characteristics such as obesity and blood neutrophils associate with poor asthma control and higher doses of inhaled corticosteroids.

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Key Words

• Body mass index
• Eosinophils
• Epidemiology
• Follow-up studies
• Neutrophils
• Sweden

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MESH Headings

• Humans
• Adult
• Neutrophils
• Obesity, Morbid/complications
• Nitric Oxide/therapeutic use
• Asthma/drug therapy
• Eosinophils
• Obesity/complications

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Affiliation(s)

Sofia Winsa-Lindmark Umeå University, Department of Public Health and Clinical Medicine, Section for Sustainable Health/The OLIN Unit, Sweden.
Caroline Stridsman Umeå University, Department of Public Health and Clinical Medicine, The OLIN Unit, Sweden
Axel Sahlin Umeå University, Department of Public Health and Clinical Medicine, Section for Sustainable Health/The OLIN Unit, Sweden
Linnea Hedman Umeå University, Department of Public Health and Clinical Medicine, Section for Sustainable Health/The OLIN Unit, Sweden
Nikolai Stenfors Umeå University, Department of Public Health and Clinical Medicine, The OLIN Unit, Sweden
Tomi Myrberg Umeå University, Department of Surgical and Perioperative Sciences, Anesthesiology and Intensive Care Medicine, Sweden
Anne Lindberg Umeå University, Department of Public Health and Clinical Medicine, The OLIN Unit, Sweden
Eva Rönmark Umeå University, Department of Public Health and Clinical Medicine, Section for Sustainable Health/The OLIN Unit, Sweden
Helena Backman Umeå University, Department of Public Health and Clinical Medicine, Section for Sustainable Health/The OLIN Unit, Sweden

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Lung Function and Asthma Clinical Control in N-ERD Patients, Three-Year Follow-Up in the Context of Real-World Evidence

Purpose

To describe the lung function and clinical control of asthma in patients with N-ERD during three years of medical follow-up using GINA guidelines.

Methods

We evaluated 75 N-ERD and 68 asthma patients (AG). Clinical control, lung function, and asthma treatment were evaluated according to GINA-2014. We compared all variables at baseline and one, two, and three years after treatment.

Results

At baseline, the N-ERD group had better basal lung function (LF) than the AG group (p<0.01), and the AG group used higher doses of inhaled corticosteroids than the N-ERD group (52.4% vs 30.5%, p=0.01) and short-term oral corticosteroid (OCS) use (52.4% vs 30.5%, p<0.01). Instead, N-ERD patients needed more use of leukotriene receptor antagonists (LTRA) (29.3% vs 5.9%, p<0.01). This group had better clinical control than the AG group (62.1% vs 34.1%, p<0.01). During the medical follow-up, the LF of the N-ERD group remained at normal values; however, these parameters improved in AG from one year (p<0.01). Likewise, there was a diminished use of high doses of ICS (52.4% vs 33%, p<0.05) and short-term OCS (67.6% vs 20.6%, p<0.01) in asthma patients. However, N-ERD patients still needed more use of LTRAs (p<0.02) during the study. In this context, one-third of N-ERD patients had to use a combination of two drugs to maintain this control. From the second year on, clinical control of asthma was similar in both groups (p>0.05).

Conclusion

According to GINA guidelines, only one-third of patients with N-ERD can gradually achieve adequate lung function and good asthma control with a high ICS dosage. Only a very small portion of patients will require the continued use of a second medication as an LTRA to keep their asthma under control.

Clinical impact of obesity on oscillometry lung mechanics in adults with asthma

BACKGROUND

In the year 2035, projections have estimated that 5% of the Scottish population will be morbidly obese defined as a body mass index (BMI) greater than or equal to 40 kg/m2. Airway oscillometry is an effort-independent test akin to bronchial sonar which measures resistance and compliance.

OBJECTIVE

To evaluate the impact of obesity on lung mechanics using oscillometry.

METHODS

Clinical data for 188 patients with respiratory physician-diagnosed moderate-to-severe asthma were retrospectively collected and analyzed.

RESULTS

Obesity (BMI 30-39.9 kg/m2) and morbid obesity (BMI ≥ 40 kg/m2) were associated with a significantly worse heterogeneity of peripheral resistance between 5 Hz and 20 Hz and peripheral compliance as low-frequency reactance at 5 Hz and area under the reactance curve, as compared with normal weight (BMI 18.5-24.9 kg/m2). Cluster analysis incorporating oscillometry identified a patient cohort who was older, obese, and female with combined impairment of spirometry and oscillometry coupled with more frequent severe exacerbations.

CONCLUSION

Obesity is associated with worse peripheral airway dysfunction in moderate-to-severe asthma, including a patient cluster who was older, obese, and female with more frequent exacerbations.

Management of comorbidities in difficult and severe asthma

Difficult-to-treat and severe asthma are challenging clinical entities. In the face of suboptimal asthma control, the temptation for clinicians is to reflexively escalate asthma-directed therapy, including increasing exposure to corticosteroids and commencement of costly but potent biologic therapies. However, asthma control is objectively and subjectively assessed based on measurable parameters (such as exacerbations or variability in pulmonary physiology), symptoms and patient histories. Crucially, these features can be confounded by common untreated comorbidities, affecting clinicians' assessment of asthma treatment efficacy.

Childhood asthma phenotypes and endotypes: a glance into the mosaic

BACKGROUND

Asthma is an inflammatory lung disease that constitutes the most common noncommunicable chronic disease in childhood. Childhood asthma shows large heterogeneity regarding onset of disease, symptoms, severity, prognosis, and response to therapy.

MAIN BODY

Evidence suggests that this variability is due to distinct pathophysiological mechanisms, which has led to an exhaustive research effort to understand and characterize these distinct entities currently designated as "endotypes." Initially, studies focused on identifying specific groups using clinical variables yielding different "clinical phenotypes." In addition, the identification of specific patterns based on inflammatory cell counts and cytokine data has resulted in "inflammatory endotypes." More recently, an increasing number of molecular data from high-throughput technology ("omics" data) have allowed to investigate more complex "molecular endotypes."

CONCLUSION

A better definition and comprehension of childhood asthma heterogeneity is key for improving diagnosis and treatment. This review aims at summarizing the current knowledge on this topic and discusses some limitations in their application as well as recommendations for future studies.

[The profile of severe asthmatics: Results from a specialized asthma clinic]

Introduction

In patients with severe asthma, individualized treatment, and appropriate phenotyping are required to achieve control. In our study, our aim was to examine the characteristics of a specific patient group in a specialized tertiary asthma outpatient clinic, which is the primary setting for evaluating severe asthma patients, with the intention of obtaining national data.

Materials and Methods

In this cross-sectional observational study, sociodemographic, clinical presentations, laboratory results, and spirometry measurements of patients with severe asthma who were followed up in our specialized asthma outpatient clinic for at least one year were recorded. Patients were defined as eosinophilic if they had a blood eosinophil count of 300/µL or higher at least twice during the oral corticosteroid free-period or 150/µL or higher under oral corticosteroids as allergic if they had sensitization to at least one inhalant allergen consistent with their history.

Result

Overall, 201 severe asthma patients (74.1% female) with a median disease duration of 15 (min-max= 1-49) years and a median follow-up duration of 7 (min-max= 1-40) years were analyzed. Most of the patients (56.7%) had adult-onset asthma [median age of onset was 32 (min-max= 10-62) years]. Overweight and obese patients were in the majority (31.8%, and 41.8%, respectively) and the median body mass index was 29 (min-max= 17.5-49.5). More than half of the patients (55.2%) had controlled asthma and the median Asthma Control Test score at the last visit was 23. Biologic therapies were applied to 73.1% (n= 147) of the patients [60.5% (n= 89) omalizumab, 39.5% (n= 58) mepolizumab]. Half of the group was allergic (49.3%) and three-quarters of them were eosinophilic (72.1%). Allergic patients had earlier asthma onset and had more controlled disease than nonallergic ones. Eosinophilic patients were younger and less obese than noneosinophilic patients. Obese and late-onset asthmatics had more uncontrolled disease than normal weight subjects and early onset patients.

Conclusions

The high rate of disease control in the patients with severe asthma in the current study demonstrated the importance of targeted individualized therapy with accurate phenotyping in specialized asthma outpatient clinics.

Meta-omics profiling of the gut-lung axis illuminates metabolic networks and host-microbial interactions associated with elevated lung elastance in a murine model of obese allergic asthma

Obesity and associated changes to the gut microbiome worsen airway inflammation and hyperresponsiveness in asthma. Obesogenic host-microbial metabolomes have altered production of metabolites that may influence lung function and inflammatory responses in asthma. To understand the interplay of the gut microbiome, metabolism, and host inflammation in obesity-associated asthma, we used a multi-omics approach to profile the gut-lung axis in the setting of allergic airway disease and diet-induced obesity. We evaluated an immunomodulator, nitro-oleic acid (NO₂-OA), as a host- and microbial-targeted treatment intervention for obesity-associated allergic asthma. Allergic airway disease was induced using house dust mite and cholera toxin adjuvant in C57BL6/J mice with diet-induced obesity to model obesity-associated asthma. Lung function was measured by flexiVent following a week of NO₂-OA treatment and allergen challenge. 16S rRNA gene (from DNA, taxa presence) and 16S rRNA (from RNA, taxa activity) sequencing, metabolomics, and host gene expression were paired with a Treatment-Measured-Response model as a data integration framework for identifying latent/hidden relationships with linear regression among variables identified from high-dimensional meta-omics datasets. Targeting both the host and gut microbiota, NO₂-OA attenuated airway inflammation, improved lung elastance, and modified the gut microbiome. Meta-omics data integration and modeling determined that gut-associated inflammation, metabolites, and functionally active gut microbiota were linked to lung function outcomes. Using Treatment-Measured-Response modeling and meta-omics profiling of the gut-lung axis, we uncovered a previously hidden network of interactions between gut levels of amino acid metabolites involved in elastin and collagen synthesis, gut microbiota, NO₂-OA, and lung elastance. Further targeted metabolomics analyses revealed that obese mice with allergic airway disease had higher levels of proline and hydroxyproline in the lungs. NO₂-OA treatment reduced proline biosynthesis by downregulation of pyrroline-5-carboxylate reductase 1 (PYCR1) expression. These findings are relevant to human disease: adults with mild-moderate asthma and BMI ≥ 25 had higher plasma hydroxyproline levels. Our results suggest that changes to structural proteins in the lung airways and parenchyma may contribute to heightened lung elastance and serve as a potential therapeutic target for obese allergic asthma.

Cluster analysis of patients with chronic rhinosinusitis and asthma after endoscopic sinus surgery

BACKGROUND

Patients with chronic rhinosinusitis with nasal polyps and asthma (CRSwAS) are highly heterogenous in severity and prognosis. The clinical phenotypes and inflammatory endotypes of CRSwAS and their association with outcomes of endoscopic sinus surgery (ESS) have not been fully studied yet.

OBJECTIVE

We aimed to find out the clinical phenotypes of CRSwAS and explore their relationship with ESS outcomes using cluster analysis.

METHODS

We recruited 103 consecutive adult patients with CRSwAS who had undergone ESS and been followed up for more than 1 year. For cluster analysis, we collected the data from 63 variables pertaining to demographic characteristics, preoperative disease status, surgical techniques, postoperative medical treatment, and outcomes. Eosinophilic CRS was defined as greater than or equal to 10 eosinophils/high-power field, and sinus computed tomography was evaluated by Lund-Mackay sinus computed tomography score (LM score).

RESULTS

We screened 92 eligible patients and 13 preoperative variables for balanced iterative reducing and clustering using hierarchies cluster analysis. Patients with CRSwAS were divided into 4 clusters with distinct ESS outcomes: (1) cluster 1, characterized by aspirin-exacerbated respiratory disease, eosinophilic CRS, high preoperative LM score, moderate-to-severe asthma, and uncontrolled CRS after ESS; (2) cluster 2, characterized as having female dominance (66.67%), non-aspirin-exacerbated respiratory disease, eosinophilic CRS, high preoperative LM score, moderate-to-severe asthma, and uncontrolled CRS after ESS; (3) cluster 3, characterized as having female dominance (95.83%), noneosinophilic CRS, low preoperative LM score, moderate asthma, and controlled CRS after ESS; and (4) cluster 4, characterized as men-only, smoker, noneosinophilic CRS, low preoperative LM score, mild asthma, and controlled CRS after ESS.

CONCLUSION

CRSwAS has distinct clusters, each corresponding to unique clinical and inflammatory characteristics and ESS outcomes.

Comparing asthma control assessment using the Asthma Control Test and the Asthma APGAR in African American/Black and Hispanic/Latinx populations

INTRODUCTION

The objective of this analysis was to compare the Asthma Control Test (ACT) and the Asthma APGAR asthma control assessment tools in African-Ancestry/Black (AA/B) and Hispanic/Latinx (H/L) adults with moderate to severe asthma.

METHODS

This pre-planned sub-study of the PREPARE clinical trial compares the baseline ACT and Asthma APGAR scores for the PREPARE populations using correlation coefficients, generalized linear modeling and receiver operating curve (ROC) analyses. Correlations were also assessed for both control tests and the Asthma Symptom Utility Index (ASUI).

RESULTS

Among the 1201 adults (603 AA/B and 598 H/L) with moderate to severe asthma, most had uncontrolled asthma by both the ACT and the Asthma APGAR. Correlation coefficients between the ACT, Asthma APGAR and ASUI were strong and did not differ significantly by race/ethnicity. The ACT consistently assessed more patients as uncontrolled compared with the Asthma APGAR. The differences in ACT and Asthma APGAR scores did not differ by age, gender, race/ethnicity, self-reported health literacy or medication adherence but did differ by education level. Both the ACT and Asthma APGAR had similar ROCs for predicting an asthma exacerbation in the next 3 months.

CONCLUSIONS

Both the ACT and the Asthma APGAR can be used for asthma control assessment in AA/B and H/L populations with moderate to severe asthma, providing comparable rates of uncontrolled asthma and similar limited ability to predict exacerbations. Further work is required to better understand the basis and clinical implications of the higher rates of uncontrolled asthma identified using the ACT.

Mitoquinone mesylate attenuates pathological features of lean and obese allergic asthma in mice

Obesity is associated with severe, difficult-to-control asthma, and increased airway oxidative stress. Mitochondrial reactive oxygen species (mROS) are an important source of oxidative stress in asthma, leading us to hypothesize that targeting mROS in obese allergic asthma might be an effective treatment. Using a mouse model of house dust mite (HDM)-induced allergic airway disease in mice fed a low- (LFD) or high-fat diet (HFD), and the mitochondrial antioxidant MitoQuinone (MitoQ), we investigated the effects of obesity and ROS on HDM-induced airway inflammation, remodeling, and airway hyperresponsiveness (AHR). Obese allergic mice showed increased lung tissue eotaxin, airway tissue eosinophilia, and AHR compared with lean allergic mice. MitoQ reduced airway inflammation, remodeling, and hyperreactivity in both lean and obese allergic mice, and tissue eosinophilia in obese-allergic mice. Similar effects were observed with decyl triphosphonium (dTPP+), the hydrophobic cationic moiety of MitoQ lacking ubiquinone. HDM-induced oxidative sulfenylation of proteins was increased particularly in HFD mice. Although only MitoQ reduced sulfenylation of proteins involved in protein folding in the endoplasmic reticulum (ER), ER stress was attenuated by both MitoQ and dTPP+ suggesting the anti-allergic effects of MitoQ are mediated in part by effects of its hydrophobic dTPP+ moiety reducing ER stress. In summary, oxidative signaling is an important mediator of allergic airway disease. MitoQ, likely through reducing protein oxidation and affecting the UPR pathway, might be effective for the treatment of asthma and specific features of obese asthma.

Effect of Azithromycin on Exacerbations in Asthma Patients with Obesity: Protocol for a Multi-Center, Prospective, Single-Arm Intervention Study

INTRODUCTION

Obesity is associated with severe asthma, but no specific treatment has been established. The gut microbiome is increasingly recognized as a crucial factor, but specific treatments focused on the gut microbiome have not been established. Recently, azithromycin has been found to have the capacity to attenuate exacerbations, a characteristic of severe asthma. The effect of azithromycin on obesity-induced severe asthma is not understood.

METHODS

The purpose of the present study is to clarify the effect of azithromycin on exacerbations in asthmatic patients with obesity. To explore the mechanism, the gut microbiome, metabolites of microbes such as short-chain fatty acids, and blood inflammatory cytokines will be analyzed to evaluate the correlation with the effect of azithromycin on exacerbations in obesity-induced severe asthma. A multi-center, prospective, single-arm intervention study is planned.

DISCUSSION

The present study will allow us to evaluate the effect of azithromycin on exacerbations, particularly in asthma patients with obesity, and explore biomarkers, targeting molecules including the gut microbiome, which are correlated with decreased exacerbations. The present results could contribute to identifying new therapeutic prospects and targeted microbes or molecules associated with severe clinical characteristics in asthmatic patients with obesity.

TRIAL REGISTRATION

This study has been registered as a prospective study with the University Hospital Medical Information Network (UMIN0000484389) and the Japan Registry of Clinical Trials (jRCTs071220023).

Classifications of moderate to severe asthma phenotypes in Japan and analysis of serum biomarkers: A Nationwide Cohort Study in Japan (NHOM Asthma Study)

BACKGROUND

Asthma is a heterogeneous disease, and phenotyping can facilitate understanding of disease pathogenesis and direct appropriate asthma treatment. This nationwide cohort study aimed to phenotype asthma patients in Japan and identify potential biomarkers to classify the phenotypes.

METHODS

Adult asthma patients (n = 1925) from 27 national hospitals in Japan were enrolled and divided into Global Initiative for Asthma (GINA) steps 4 or 5 (GINA 4, 5) and GINA Steps 1, 2, or 3 (GINA 1-3) for therapy. Clinical data and questionnaires were collected. Biomarker levels among GINA 4, 5 patients were measured. Ward's minimum variance hierarchical clustering method and tree analysis were performed for phenotyping. Analysis of variance, the Kruskal-Wallis, and chi-square tests were used to compare cluster differences.

RESULTS

The following five clusters were identified: 1) late-onset, old, less-atopic; 2) late-onset, old, eosinophilic, low FEV₁; 3) early-onset, long-duration, atopic, poorly controlled; 4) early-onset, young, female-dominant, atopic; and 5) female-dominant, T1/T2-mixed, most severe. Age of onset, disease duration, blood eosinophils and neutrophils, asthma control questionnaire Sum 6, number of controllers, FEV₁, body mass index (BMI), and hypertension were the phenotype-classifying variables determined by tree analysis that assigned 79.5% to the appropriate cluster. Among the cytokines measured, IL-1RA, YKL40/CHI3L1, IP-10/CXCL10, RANTES/CCL5, and TIMP-1 were useful biomarkers for classifying GINA 4, 5 phenotypes.

CONCLUSIONS

Five distinct phenotypes were identified for moderate to severe asthma and may be classified using clinical and molecular variables (Registered in UMIN-CTR; UMIN000027776.).

Determinants of Severe Asthma - A Long-Term Cohort Study in Northern Sweden

Background

Risk factors for severe asthma are not well described. The aim was to identify clinical characteristics and risk factors at study entry that are associated with severe asthma at follow-up in a long-term prospective population-based cohort study of adults with asthma.

Methods

Between 1986 and 2001, 2055 adults with asthma were identified by clinical examinations of population-based samples in northern Sweden. During 2012-2014, n = 1006 (71% of invited) were still alive, residing in the study area and participated in a follow-up, of which 40 were identified as having severe asthma according to ERS/ATS, 131 according to GINA, while 875 had other asthma. The mean follow-up time was 18.7 years.

Results

Obesity at study entry and adult-onset asthma were associated with severe asthma at follow-up. While severe asthma was more common in those with adult-onset asthma in both men and women, the association with obesity was observed in women only. Sensitization to mites and moulds, but not to other allergens, as well as NSAID-related respiratory symptoms was more common in severe asthma than in other asthma. Participants with severe asthma at follow-up had lower FEV₁, more pronounced FEV₁ reversibility, and more wheeze, dyspnea and nighttime awakenings already at study entry than those with other asthma.

Conclusion

Adult-onset asthma is an important risk factor for development of severe asthma in adults, and obesity increased the risk among women. The high burden of respiratory symptoms already at study entry also indicate long-term associations with development of severe asthma.

Leukocyte redistribution as immunological biomarker of corticosteroid resistance in severe asthma

BACKGROUND

Earlier studies have suggested that the leukocyte redistribution can be considered as an immunological marker of the clinical response to corticosteroids (CS), representing an easy measurable potential biomarker in severe asthma.

OBJECTIVE

The aim of this study was to determinate the utility of the leukocyte redistribution as a biomarker of disease heterogeneity in patients with severe asthma and as a bioindicator of potential CS resistance.

METHODS

We developed an unbiased clustering approach based on the clinical data and the flow cytometry results of peripheral blood leukocyte phenotypes of 142 patients with severe asthma before and after systemic CS administration.

RESULTS

Based on the differences in the blood count eosinophils, neutrophils and lymphocytes, together with the flow cytometry measurements of basic T cell, B cell and NK cell subpopulations before and after systemic CS administration, we identified two severe asthma clusters, which differed in the cell frequencies, response to CS and atopy status. Patients in cluster 1 had higher frequency of blood eosinophils at baseline, were sensitized to less allergens and had better steroid responsiveness, measured as the pronounced leukocyte redistribution after the administration of systemic CS. Patients in cluster 2 were determined by the higher frequency of B-cells and stronger IgE sensitization status to the multiple allergens. They also displayed higher steroid resistance, as the clinical correlate for the lower leukocyte redistribution after administration of systemic CS.

CONCLUSION

The flow cytometry-based profiling of the basic populations of immune cells in the blood and its analysis before and after systemic corticosteroid administration could improve personalized treatment approaches in patients with severe asthma.

Obesity affects pulmonary function in Japanese adult patients with asthma, but not those without asthma

Obesity is associated with the severity of asthma, which is characterized by airway obstruction. Pulmonary function testing is one of the important examinations for evaluating airway obstruction. However, the impact of obesity on pulmonary function in patients with asthma is not fully understood. A total of 193 patients with asthma and 2159 patients without asthma who visited Saga University Hospital were investigated retrospectively. Obesity was defined as a body mass index (BMI) greater than 25 kg/m². Pulmonary functions including forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV₁) were compared between patients with and without asthma, focusing especially on obesity. FVC percent predicted and FEV₁ percent predicted were significantly lower in patients with asthma than in those without asthma (p = 0.03, < 0.01 respectively). In patients with asthma, FVC percent predicted and FEV₁ percent predicted were significantly lower in patients with obesity than in those without obesity (all p < 0.01). In addition, BMI was negatively correlated with FEV₁ (r =- 0.21, p = 0.003) and FVC (r = - 0.15, p = 0.04), along with the percent predicted. On multivariate analysis in patients with asthma, FVC (β [95% confidence interval] 0.12 [0.02-0.22], p = 0.02) and FEV₁ (0.13 [0.05-0.22], p < 0.01) were still significantly different between patients with and without obesity. However, these obesity-associated differences were not observed in patients without asthma. Obesity reduces pulmonary function, including FVC and FEV₁, in patients with asthma, but not in those without asthma.

Asthma clustering methods: a literature-informed application to the children's health study data

OBJECTIVE

The heterogeneity of asthma has inspired widespread application of statistical clustering algorithms to a variety of datasets for identification of potentially clinically meaningful phenotypes. There has not been a standardized data analysis approach for asthma clustering, which can affect reproducibility and clinical translation of results. Our objective was to identify common and effective data analysis practices in the asthma clustering literature and apply them to data from a Southern California population-based cohort of schoolchildren with asthma.

METHODS

As of January 1, 2020, we reviewed key statistical elements of 77 asthma clustering studies. Guided by the literature, we used 12 input variables and three clustering methods (hierarchical clustering, k-medoids, and latent class analysis) to identify clusters in 598 schoolchildren with asthma from the Southern California Children's Health Study (CHS).

RESULTS

Clusters of children identified by latent class analysis were characterized by exhaled nitric oxide, FEV1/FVC, FEV1 percent predicted, asthma control and allergy score; and were predictive of control at two year follow up. Clusters from the other two methods were less clinically remarkable, primarily differentiated by sex and race/ethnicity and less predictive of asthma control over time.

CONCLUSION

Upon review of the asthma phenotyping literature, common approaches of data clustering emerged. When applying these elements to the Children's Health Study data, latent class analysis clusters-represented by exhaled nitric oxide and spirometry measures-had clinical relevance over time.

Body Composition-Specific Asthma Phenotypes: Clinical Implications

Background: Previous studies have indicated the limitations of body mass index for defining disease phenotypes. The description of asthma phenotypes based on body composition (BC) has not been largely reported. Objective: To identify and characterize phenotypes based on BC parameters in patients with asthma. Methods: A study with two prospective observational cohorts analyzing adult patients with stable asthma (n = 541 for training and n = 179 for validation) was conducted. A body composition analysis was performed for the included patients. A cluster analysis was conducted by applying a 2-step process with stepwise discriminant analysis. Logistic regression models were used to evaluate the association between identified phenotypes and asthma exacerbations (AEs). The same algorithm for cluster analysis in the independent validation set was used to perform an external validation. Results: Three clusters had significantly different characteristics associated with asthma outcomes. An external validation identified the similarity of the participants in training and the validation set. In the training set, cluster Training (T) 1 (29.4%) was “patients with undernutrition”, cluster T2 (18.9%) was “intermediate level of nutrition with psychological dysfunction”, and cluster T3 (51.8%) was “patients with good nutrition”. Cluster T3 had a decreased risk of moderate-to-severe and severe AEs in the following year compared with the other two clusters. The most important BC-specific factors contributing to being accurately assigned to one of these three clusters were skeletal muscle mass and visceral fat area. Conclusion: We defined three distinct clusters of asthma patients, which had distinct clinical features and asthma outcomes. Our data reinforced the importance of evaluating BC to determining nutritional status in clinical practice.

Neutrophils and Asthma

Although eosinophilic inflammation is characteristic of asthma pathogenesis, neutrophilic inflammation is also marked, and eosinophils and neutrophils can coexist in some cases. Based on the proportion of sputum cell differentiation, asthma is classified into eosinophilic asthma, neutrophilic asthma, neutrophilic and eosinophilic asthma, and paucigranulocytic asthma. Classification by bronchoalveolar lavage is also performed. Eosinophilic asthma accounts for most severe asthma cases, but neutrophilic asthma or a mixture of the two types can also present a severe phenotype. Biomarkers for the diagnosis of neutrophilic asthma include sputum neutrophils, blood neutrophils, chitinase-3-like protein, and hydrogen sulfide in sputum and serum. Thymic stromal lymphoprotein (TSLP)/T-helper 17 pathways, bacterial colonization/microbiome, neutrophil extracellular traps, and activation of nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 pathways are involved in the pathophysiology of neutrophilic asthma and coexistence of obesity, gastroesophageal reflux disease, and habitual cigarette smoking have been associated with its pathogenesis. Thus, targeting neutrophilic asthma is important. Smoking cessation, neutrophil-targeting treatments, and biologics have been tested as treatments for severe asthma, but most clinical studies have not focused on neutrophilic asthma. Phosphodiesterase inhibitors, anti-TSLP antibodies, azithromycin, and anti-cholinergic agents are promising drugs for neutrophilic asthma. However, clinical research targeting neutrophilic inflammation is required to elucidate the optimal treatment.

Association of mold levels in urban children's homes with difficult-to-control asthma

BACKGROUND

Mold sensitization and exposure are associated with asthma severity, but the specific species that contribute to difficult-to-control (DTC) asthma are unknown.

OBJECTIVE

We sought to determine the association between overall and specific mold levels in the homes of urban children and DTC asthma.

METHODS

The Asthma Phenotypes in the Inner-City study recruited participants, aged 6 to 17 years, from 8 US cities and classified each participant as having either DTC asthma or easy-to-control (ETC) asthma on the basis of treatment step level. Dust samples had been collected in each participant's home (n = 485), and any dust remaining (n = 265 samples), after other analyses, was frozen at -20^oC. The dust samples (n = 265) were analyzed using quantitative PCR to determine the concentrations of the 36 molds in the Environmental Relative Moldiness Index. Logistic regression was performed to discriminate specific mold content of dust from homes of children with DTC versus ETC asthma.

RESULTS

Frozen-dust samples were available from 54% of homes of children with DTC (139 of 253) and ETC asthma (126 of 232). Only the average concentration of the mold Mucor was significantly (P < .001) greater in homes of children with DTC asthma. In homes with window air-conditioning units, the Mucor concentration contributed about a 22% increase (1.6 odds ratio; 95% CI, 1.2-2.2) in the ability to discriminate between cases of DTC and ETC asthma.

CONCLUSIONS

Mucor levels in the homes of urban youth were a predictor of DTC asthma, and these higher Mucor levels were more likely in homes with a window air-conditioner.

Trajectories of asthma and allergy symptoms from childhood to adulthood

BACKGROUND

Phenotypes of asthma and allergic diseases are mainly studied separately for children and adults. To explore the role of adolescence and young adulthood, we investigated symptom trajectories at the transition from childhood into adulthood.

METHODS

Latent class analysis (LCA) was conducted in a population initially recruited for the German arm of Phase II of the International Study of Asthma and Allergies in Childhood and followed-up three times until their early 30s (N=2267). Indicators included in LCA were 12-month prevalences of symptoms of wheeze, rhinoconjunctivitis, and eczema. Latent classes were further characterised regarding important traits such as skin prick tests. Logistic regression models were used to investigate associations with environmental determinants such as smoking and occupational exposures.

RESULTS

Six latent classes were identified: an asymptomatic one as well as three with single and two with co-occurring symptoms. All trajectories essentially established between baseline assessment at around 10 years and the first follow-up at around 17 years. Probabilities for symptoms increased from childhood to adolescence, especially for wheeze-related latent classes, while they remained constant in adulthood. Wheeze-related latent classes were also positively associated with exposures during adolescence (e.g. active smoking).

CONCLUSION

Distinct trajectories of asthma and allergy symptoms establish from childhood through adolescence and stabilize during early adulthood. This pattern was most notable in wheeze-related latent classes which also showed the strongest positive associations with environmental exposures in adolescence/young adulthood. Therefore, not only childhood but also adolescence is relevant for disease development and offers considerable potential for prevention and health promotion.

Therapeutic ketosis decreases methacholine hyperresponsiveness in mouse models of inherent obese asthma

Obese asthmatics tend to have severe, poorly controlled disease and exhibit methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility. Substantial weight loss in obese asthmatics or in mouse models of the condition decreases methacholine hyperresponsiveness. Ketone bodies are rapidly elevated during weight loss, coinciding with or preceding relief from asthma-related comorbidities. As ketone bodies may exert numerous potentially therapeutic effects, augmenting their systemic concentrations is being targeted for the treatment of several conditions. Circulating ketone body levels can be increased by feeding a ketogenic diet or by providing a ketone ester dietary supplement, which we hypothesized would exert protective effects in mouse models of inherent obese asthma. Weight loss induced by feeding a low-fat diet to mice previously fed a high-fat diet was preceded by increased urine and blood levels of the ketone body β-hydroxybutyrate (BHB). Feeding a ketogenic diet for 3 wk to high-fat diet-fed obese mice or genetically obese db/db mice increased BHB concentrations and decreased methacholine hyperresponsiveness without substantially decreasing body weight. Acute ketone ester administration decreased methacholine responsiveness of normal mice, and dietary ketone ester supplementation of high-fat diet-fed mice decreased methacholine hyperresponsiveness. Ketone ester supplementation also transiently induced an "antiobesogenic" gut microbiome with a decreased Fermicutes/Bacteroidetes ratio. Dietary interventions to increase systemic BHB concentrations could provide symptom relief for obese asthmatics without the need for the substantial weight loss required of patients to elicit benefits to their asthma through bariatric surgery or other diet or lifestyle alterations.

Evaluating the glucagon-like peptide-1 receptor in managing asthma

PURPOSE OF REVIEW

The aim of this study was to discuss the role of glucagon-like peptide-1 (GLP-1) receptor signalling in reducing lung inflammation and potential use for GLP-1 receptor agonists (GLP-1RAs) in management of asthma.

RECENT FINDINGS

Although GLP-1RA are currently used for the treatment of type 2 diabetes (T2D) and weight loss in obesity, there is much interest in expanding the indications for use in other diseases, including inflammatory pulmonary disease. In animal models of both acute and chronic pulmonary disease, use of GLP-1RA reduces airway inflammation, obstruction and fibrosis. In particular, GLP-1 receptor (GLP-1R) signalling seems to inhibit allergen-induced type 2 inflammation, making it an attractive agent for asthma. Results are especially promising in disease processes with disturbed metabolic regulation, such as T2D or metabolic syndrome. Retrospective clinical studies demonstrate promising evidence for the use of GLP-1RAs in comorbid diabetes and asthma, although prospective human studies are limited.

SUMMARY

Here, we discuss the biology of GLP-1 and GLP-1R signalling, review the preclinical and mechanistic evidence for how GLP-1R signalling may reduce pulmonary inflammation, and summarize recent and upcoming clinical studies. Ultimately, targeting GLP-1R signalling may represent a novel approach for asthma therapy that is glucocorticoid sparing and possibly disease modifying.

The Precision Interventions for Severe and/or Exacerbation-Prone (PrecISE) Asthma Network: An overview of Network organization, procedures, and interventions

Asthma is a heterogeneous disease, with multiple underlying inflammatory pathways and structural airway abnormalities that impact disease persistence and severity. Recent progress has been made in developing targeted asthma therapeutics, especially for subjects with eosinophilic asthma. However, there is an unmet need for new approaches to treat patients with severe and exacerbation-prone asthma, who contribute disproportionately to disease burden. Extensive deep phenotyping has revealed the heterogeneous nature of severe asthma and identified distinct disease subtypes. A current challenge in the field is to translate new and emerging knowledge about different pathobiologic mechanisms in asthma into patient-specific therapies, with the ultimate goal of modifying the natural history of disease. Here, we describe the Precision Interventions for Severe and/or Exacerbation-Prone Asthma (PrecISE) Network, a groundbreaking collaborative effort of asthma researchers and biostatisticians from around the United States. The PrecISE Network was designed to conduct phase II/proof-of-concept clinical trials of precision interventions in the population with severe asthma, and is supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health. Using an innovative adaptive platform trial design, the PrecISE Network will evaluate up to 6 interventions simultaneously in biomarker-defined subgroups of subjects. We review the development and organizational structure of the PrecISE Network, and choice of interventions being studied. We hope that the PrecISE Network will enhance our understanding of asthma subtypes and accelerate the development of therapeutics for severe asthma.

Involvement of autophagy in exacerbation of eosinophilic airway inflammation in a murine model of obese asthma

Obesity is a common comorbidity in patients with asthma, and obese asthma patients present the most refractory phenotype among patients with severe asthma. Similar to the observations in non-obese asthma patients, clinical studies have revealed heterogeneity in obese asthma patients, including the occurrences of T helper (Th)2-high and Th2-low phenotypes. However, the mechanisms underlying obesity-related asthma are not completely understood. Though macroautophagy/autophagy is involved in asthma and obesity, its role in obesity-associated asthma is unknown. We hypothesized that autophagy is involved in the pathogenesis of obese asthma. For our investigations, we used high-fat diet-induced Atg5 (autophagy related 5)-deficient mice and epithelial cell-specific atg5^−/− (Scgb1a1/CCSP-atg5^−/−) obesity-induced mice. House dust mite (HDM)-sensitized atg5^−/− obese mice exhibited marked eosinophilic inflammation and airway hyper-reactivity (AHR), compared to wild-type (WT) obese mice. Analyses of atg5^−/− obese mice showed increased levels of Th2 cells but not ILC2s together with elevated expression of Th2 cytokines in the lung. In response to the HDM challenge, activated epithelial autophagy was observed in lean but not obese WT mice. Epithelium-specific deletion of Atg5 induced eosinophilic inflammation in Scgb1a1/CCSP-atg5^−/− obese mice, and genetic analyses of epithelial cells from HDM-immunized atg5^−/− obesity-induced mice showed an elevated expression of thymic stromal lymphopoietin (TSLP) and IL33. Notably, HDM-sensitized atg5^−/− mice developed TSLP- and IL33-dependent eosinophilic inflammation and AHR. Our results suggest that autophagy contributes to the exacerbation of eosinophilic inflammation in obese asthma. Modulations of autophagy may be a therapeutic target in obesity-associated asthma.

Abbreviations: AHR: airway hyper-reactivity; BAL: bronchoalveolar lavage; C_dyn: dynamic compliance; BM: bone marrow; HDM: house dust mite; HFD: high-fat diet; ILC2s: type 2 innate lymphocyte cells; ROS: reactive oxygen species; R_L: lung resistance; TSLP: thymic stromal lymphopoietin; TCC: total cell count; WT: wild type.

Stratified approaches for using biomarkers in phenotyping for the management of severe asthma in India

Various respiratory societies including the Global Initiative for Asthma (GINA), European Respiratory Society (ERS) and American Thoracic Society (ATS) define severe asthma as asthma that requires or remains uncontrolled despite treatment with systemic corticosteroids or high-dose inhaled corticosteroids plus another controller such as long acting beta agonist. The management of asthma as an entity is not straightforward due to inter-individual variability in assessment parameters. With the advent of science, targeted therapies are on the emergence for management of severe asthma. A biomarker can be used as a surrogate to phenotype a patient as well as to measure the response to therapy with any drug. Biomarkers have been critical for studies of disease pathogenesis and the development of new therapies in severe asthma. From a resource constraint perspective like countries in India, it is imperative to use biomarkers that are easily available are affordable cost. Choosing an ideal biomarkers is also important from a perspective of choosing a particular therapy. The cost associated with the biologicals is high and it is imperative to gauge the treatment effectiveness with the therapy at the earliest considering the out of pocket spends of the patients.

Metformin prevents airway hyperreactivity in rats with dietary obesity

Increased insulin is associated with obesity-related airway hyperreactivity and asthma. We tested whether the use of metformin, an anti-diabetic drug used to reduce insulin resistance, can reduce circulating insulin, thereby preventing airway hyperreactivity in rats with dietary obesity. Male and female rats were fed a high- or low-fat diet for 5 weeks. Some male rats were simultaneously treated with metformin (100 mg/kg, p.o.). In separate experiments, after 5 weeks of a high-fat diet, some rats were switched to a low-fat diet, while others continued a high-fat diet for an additional 5 weeks. Bronchoconstriction and bradycardia in response to bilateral electrical vagus nerve stimulation or to inhaled methacholine were measured in anesthetized and vagotomized rats. Body weight, body fat, caloric intake, fasting glucose and insulin were measured. Vagally-induced bronchoconstriction was potentiated only in male rats on a high-fat diet. Males gained more body weight, body fat, and had increased levels of fasting insulin, compared to females. Metformin prevented development of vagally-induced airway hyperreactivity in male rats on high-fat diet, in addition to inhibiting weight gain, fat gain and increased insulin. In contrast, switching rats to a low-fat diet for 5 weeks reduced body weight and body fat, it did not reverse fasting glucose, fasting insulin or potentiation of vagally-induced airway hyperreactivity. These data suggest that medications that target insulin may be effective treatment for obesity-related asthma.

Nitroalkene fatty acids modulate bile acid metabolism and lung function in obese asthma

Bile acid profiles are altered in obese individuals with asthma. Thus, we sought to better understand how obesity-related systemic changes contribute to lung pathophysiology. We also test the therapeutic potential of nitro-oleic acid (NO₂-OA), a regulator of metabolic and inflammatory signaling pathways, to mitigate allergen and obesity-induced lung function decline in a murine model of asthma. Bile acids were measured in the plasma of healthy subjects and individuals with asthma and serum and lung tissue of mice with and without allergic airway disease (AAD). Lung function, indices of inflammation and hepatic bile acid enzyme expression were measured in obese mice with house dust mite-induced AAD treated with vehicle or NO₂-OA. Serum levels of glycocholic acid and glycoursodeoxycholic acid clinically correlate with body mass index and airway hyperreactivity whereas murine levels of β-muricholic acid and tauro-β-muricholic acid were significantly increased and positively correlated with impaired lung function in obese mice with AAD. NO₂-OA reduced murine bile acid levels by modulating hepatic expression of bile acid synthesis enzymes, with a concomitant reduction in small airway resistance and tissue elastance. Bile acids correlate to body mass index and lung function decline and the signaling actions of nitroalkenes can limit AAD by modulating bile acid metabolism, revealing a potential pharmacologic approach to improving the current standard of care.

Pioglitazone prevents obesity-related airway hyperreactivity and neuronal M2 receptor dysfunction

Obesity-related asthma often presents with more severe symptoms than non-obesity-related asthma and responds poorly to current treatments. Both insulin resistance and hyperinsulinemia are common in obesity. We have shown that increased insulin mediates airway hyperreactivity in diet-induced obese rats by causing neuronal M2 muscarinic receptor dysfunction, which normally inhibits acetylcholine release from parasympathetic nerves. Decreasing insulin with streptozotocin prevented airway hyperreactivity and M2 receptor dysfunction. The objective of the present study was to investigate whether pioglitazone, a hypoglycemic drug, prevents airway hyperreactivity and M2 receptor dysfunction in obese rats. Male rats fed a low- or high-fat diet were treated with pioglitazone or PBS by daily gavage. Body weight, body fat, fasting insulin, and bronchoconstriction and bradycardia in response to electrical stimulation of vagus nerves and to aerosolized methacholine were recorded. Pilocarpine, a muscarinic receptor agonist, was used to measure M2 receptor function. Rats on a high-fat diet had potentiated airway responsiveness to vagal stimulation and dysfunctional neuronal M2 receptors, whereas airway responsiveness to methacholine was unaffected. Pioglitazone reduced fasting insulin and prevented airway hyperresponsiveness and M2 receptor dysfunction but did not change inflammatory cytokine mRNA expression in alveolar macrophages. High-fat diet, with and without pioglitazone, had tissue-specific effects on insulin receptor mRNA expression. In conclusion, pioglitazone prevents vagally mediated airway hyperreactivity and protects neuronal M2 muscarinic receptor function in obese rats.

Asthma Phenotypes as a Guide for Current and Future Biologic Therapies

Asthma has been increasingly recognized as being a heterogeneous disease with multiple distinct mechanisms and pathophysiologies. Evidence continues to build regarding the existence of different cell types, environmental exposures, pathogens, and other factors that produce a similar set of symptoms known collectively as asthma. This has led to a movement from a "one size fits all" symptom-based methodology to a more patient-centered, individualized approach to asthma treatment targeting the underlying disease process. A significant contributor to this shift to more personalized asthma therapy has been the increasing availability of numerous biologic therapies in recent years, providing the opportunity for more targeted treatments. When targeted biologics began to be developed for treatment of asthma, the hope was that distinct biomarkers would become available, allowing the clinician to determine which biologic therapy was best suited for which patients. Presence of certain biomarkers, like eosinophilia or antigen-specific IgE, is important features of specific asthma phenotypes. Currently available biomarkers can help with decision making about biologics, but are generally too broad and non-specific to clearly identify an asthma phenotype or the single biologic best suited to an asthmatic. Identification of further biomarkers is the subject of intense research. Yet, identifying a patient's asthma phenotype can help in predicting disease course, response to treatment, and biologic therapies to consider. In this review, major asthma phenotypes are reviewed, and the evidence for the utility of various biologics, both those currently on the market and those in the development process, in each of these phenotypes is explored.

Novel therapeutic approaches targeting endotypes of severe airway disease

Introduction: Severe asthma and chronic rhinosinusitis (CRS), with nasal polyps (CRSwNP) and without nasal polyps (CRSsNP), are heterogeneous diseases characterized by different mechanistic pathways (endotypes) and variable clinical presentations (phenotypes).Areas covered: This review provides the clinician with an overview of the prevalence and clinical impact of severe chronic upper and lower airways disease and suggests a novel therapeutic approach with biological agents with possible biomarkers. To select relevant literature for inclusion in this review, we conducted a literature search using the PubMed database, using terms 'severe airways disease' AND 'endotype' AND 'treatment.' The literature review was performed for publication years 2010-2020, restricting the articles to humans and English language publications.Expert opinion: The coronavirus disease (COVID-19) pandemic has brought forth many challenges for patients with severe airway disease and healthcare practitioners involved in care. These patients could have an increased risk of developing severe SARS-CoV-2 disease, although treatment with biologics is not associated with a worse prognosis. Eosinopenia on hospital admission plays a key role as a diagnostic and prognostic biomarker.

Association Between Environmental Factors and Asthma Using Mendelian Randomization: Increased Effect of Body Mass Index on Adult-Onset Moderate-to-Severe Asthma Subtypes

Although asthma is one of the most common chronic diseases throughout all age groups, its etiology remains unknown, primarily due to its heterogeneous characteristics. We examined the causal effects of various environmental factors on asthma using Mendelian randomization and determined whether the susceptibility to asthma due to the causal effect of a risk factor differs between asthma subtypes, based on age of onset, severity of asthma, and sex. We performed Mendelian randomization analyses (inverse variance weighted, weighted median, and generalized summary-data-based Mendelian randomization) using UK Biobank data to estimate the causal effects of 69 environmental factors on asthma. Additional sensitivity analyses (MR-Egger regression, Cochran’s Q test, clumping, and reverse Mendelian randomization) were performed to ensure minimal or no pleiotropy. For confirmation, two-sample setting analyses were replicated using BMI SNPs that had been reported by a meta-genome-wide association study in Japanese and European (GIANT) populations and a genome-wide association study in control individuals from the UK Biobank. We found that BMI causally affects the development of asthma and that the adult-onset moderate-to-severe asthma subtype is the most susceptible to causal inference by BMI. Further, it is likely that the female subtype is more susceptible to BMI than males among adult asthma cases. Our findings provide evidence that obesity is a considerable risk factor in asthma patients, particularly in adult-onset moderate-to-severe asthma cases, and that weight loss is beneficial for reducing the burden of asthma.

FASE-CPHG Study: identification of asthma phenotypes in the French Severe Asthma Study using cluster analysis

BACKGROUND

In France, data regarding epidemiology and management of severe asthma are scarce. The objective of this study was to describe asthma phenotypes using a cluster analysis in severe asthmatics recruited in a real world setting.

METHODS

The study design was prospective, observational and multicentric. The patients included were adults with severe asthma (GINA 4-5) followed-up in French Non Academic Hospital between May 2016 and June 2017. One hundred and seven physicians included 1502 patients. Both sociodemographic and clinical variables were collected. Hierarchical cluster analysis was performed by the Ward method followed by k-means cluster analysis on a population of 1424 patients.

RESULTS

Five clusters were identified: cluster 1 (n = 690, 47%) called early onset allergic asthma (47.5% with asthma before 12 years), cluster 2 (n = 153, 10.5%): obese asthma (63.5% with BMI > 30 kg/m2), cluster 3 (n = 299, 20.4%): late-onset asthma with severe obstructive syndrome (89% without atopy), cluster 4 (n = 143, 9.8%): eosinophilic asthma (51.7% had more than 500 eosinophils/mm3), and cluster 5 (n = 139, 9.5%): aspirin sensitivity asthma (63% had severe asthma attacks).

CONCLUSIONS

In our population of adults with severe asthma followed by pulmonologists, five distinct phenotypes were identified and are quite different from those mentioned in previous studies.

A Systematic Review of Asthma Phenotypes Derived by Data-Driven Methods

Classification of asthma phenotypes has a potentially relevant impact on the clinical management of the disease. Methods for statistical classification without a priori assumptions (data-driven approaches) may contribute to developing a better comprehension of trait heterogeneity in disease phenotyping. This study aimed to summarize and characterize asthma phenotypes derived by data-driven methods. We performed a systematic review using three scientific databases, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. We included studies reporting adult asthma phenotypes derived by data-driven methods using easily accessible variables in clinical practice. Two independent reviewers assessed studies. The methodological quality of included primary studies was assessed using the ROBINS-I tool. We retrieved 7446 results and included 68 studies of which 65% (n = 44) used data from specialized centers and 53% (n = 36) evaluated the consistency of phenotypes. The most frequent data-driven method was hierarchical cluster analysis (n = 19). Three major asthma-related domains of easily measurable clinical variables used for phenotyping were identified: personal (n = 49), functional (n = 48) and clinical (n = 47). The identified asthma phenotypes varied according to the sample’s characteristics, variables included in the model, and data availability. Overall, the most frequent phenotypes were related to atopy, gender, and severe disease. This review shows a large variability of asthma phenotypes derived from data-driven methods. Further research should include more population-based samples and assess longitudinal consistency of data-driven phenotypes.

Asthma Exacerbations in Patients with Type 2 Diabetes and Asthma on Glucagon-like Peptide-1 Receptor Agonists

Rationale: GLP-1R (glucagon-like peptide-1 receptor) agonists are approved to treat type 2 diabetes mellitus and obesity. GLP-1R agonists reduce airway inflammation and hyperresponsiveness in preclinical models.Objectives: To compare rates of asthma exacerbations and symptoms between adults with type 2 diabetes and asthma prescribed GLP-1R agonists and those prescribed SGLT-2 (sodium-glucose cotransporter-2) inhibitors, DPP-4 (dipeptidyl peptidase-4) inhibitors, sulfonylureas, or basal insulin for diabetes treatment intensification.Methods: This study was an electronic health records-based new-user, active-comparator, retrospective cohort study of patients with type 2 diabetes and asthma newly prescribed GLP-1R agonists or comparator drugs at an academic healthcare system from January 2000 to March 2018. The primary outcome was asthma exacerbations; the secondary outcome was encounters for asthma symptoms. Propensity scores were calculated for GLP-1R agonist and non-GLP-1R agonist use. Zero-inflated Poisson regression models included adjustment for multiple covariates.Measurements and Main Results: Patients initiating GLP-1R agonists (n = 448), SGLT-2 inhibitors (n = 112), DPP-4 inhibitors (n = 435), sulfonylureas (n = 2,253), or basal insulin (n = 2,692) were identified. At 6 months, asthma exacerbation counts were lower in persons initiating GLP-1R agonists (reference) compared with SGLT-2 inhibitors (incidence rate ratio [IRR], 2.98; 95% confidence interval [CI], 1.30-6.80), DPP-4 inhibitors (IRR, 2.45; 95% CI, 1.54-3.89), sulfonylureas (IRR, 1.83; 95% CI, 1.20-2.77), and basal insulin (IRR, 2.58; 95% CI, 1.72-3.88). Healthcare encounters for asthma symptoms were also lower among GLP-1R agonist users.Conclusions: Adult patients with asthma prescribed GLP-1R agonists for type 2 diabetes had lower counts of asthma exacerbations compared with other drugs initiated for treatment intensification. GLP-1R agonists may represent a novel treatment for asthma associated with metabolic dysfunction.

Aspirin desensitization in NSAID-exacerbated respiratory disease and its outcomes in the clinical course of asthma: A systematic review of the literature and meta-analysis

Background

Nonsteroidal anti-inflammatory drug-exacerbated respiratory disease (NERD) might benefit from aspirin desensitization (AD) as an alternative treatment to standard care. However, there is conflicting evidence regarding its role in bronchial symptoms and asthma exacerbations.

Objective

To analyze the clinical effects of AD in terms of lung function, systemic and inhaled steroid use, the frequency of acute asthma exacerbations, and adverse effects in patients with NERD and asthma.

Methodology

We identified randomized clinical trials (RCTs) from PubMed, EMBASE, SCOPUS, and EBSCO. We also searched the RCT references for additional studies. Studies comparing AD to placebo in patients with a previous history of pulmonary symptoms triggered by ASA or other NSAIDs or with a positive provocation test to ASA were included.

Primary results

Five studies with 210 participants with NERD were included in this review. The study duration ranged from 3 to 6 months. Overall, the risk of bias across the included RCTs was low. We identified 3 studies evaluating lung function, 2 of which reported a significant improvement in FEV1 in the AD group after 6 months, while the other reported no difference among the treatments. Due to high heterogeneity, we did not pool the results. The remaining primary outcomes were reported only in a single study each, hindering their interpretation. Secondary outcomes revealed reduced symptom and medication scores in patients with AD.

Conclusions

Due to the small number of studies included in this systematic review, conclusions should be made with caution. AD shows a trend towards improving lung function (FEV1) following 6 months of treatment, although no conclusions can be made regarding the use of corticosteroids or the frequency of acute exacerbations. AD appears to reduce both symptom and medication scores. Additional RCTs are needed to fully assess the efficacy of AD in reducing bronchial symptoms in patients with NERD.

Cluster Analysis of Inflammatory Biomarker Expression in the International Severe Asthma Registry

BACKGROUND

Allergy, eosinophilic inflammation, and epithelial dysregulation are implicated in severe asthma pathogenesis.

OBJECTIVE

We characterized biomarker expression in adults with severe asthma.

METHODS

Within the International Severe Asthma Registry (ISAR), we analyzed data from 10 countries in North America, Europe, and Asia, with prespecified thresholds for biomarker positivity (serum IgE ≥ 75 kU/L, blood eosinophils ≥ 300 cells/μL, and FeNO ≥ 25 ppb), and with hierarchical cluster analysis using biomarkers as continuous variables.

RESULTS

Of 1,175 patients; 64% were female, age (mean ± SD) 53 ± 15 years, body mass index (BMI) 30 ± 8, postbronchodilator forced expiratory volume in 1 second (FEV₁) predicted 72% ± 20%. By prespecified thresholds, 59% were IgE positive, 57% eosinophil positive, and 58% FeNO positive. There was substantial inflammatory biomarker overlap; 59% were positive for either 2 or 3 biomarkers. Five distinct clusters were identified: cluster 1 (61%, low-to-medium biomarkers) comprised highly symptomatic, older females with elevated BMI and frequent exacerbations; cluster 2 (18%, elevated eosinophils and FeNO) older females with lower BMI and frequent exacerbations; cluster 3 (14%, extremely high FeNO) older, highly symptomatic, lower BMI, and preserved lung function; cluster 4 (6%, extremely high IgE) younger, long duration of asthma, elevated BMI, and poor lung function; cluster 5 (1.2%, extremely high eosinophils) younger males with low BMI, poor lung function, and high burden of sinonasal disease and polyposis.

CONCLUSIONS

There is significant overlap of biomarker positivity in severe asthma. Distinct clusters according to biomarker expression exhibit unique clinical characteristics, suggesting the occurrence of discrete patterns of underlying inflammatory pathway activation and providing pathogenic insights relevant to the era of monoclonal biologics.

Contribution of systemic and airway immune responses to pediatric obesity-related asthma

Childhood obesity contributes to many diseases, including asthma. Although the precise mechanism by which obesity causes asthma is not known, there is literature to suggest that innate and adaptive systemic and airway immune responses in obese children with asthma differ from those in normal-weight children with asthma. Both non-allergic or non-T2 phenotype with systemic T helper (Th)1 polarization and allergic Th cell responses have been reported in childhood obesity-related asthma. There is preliminary evidence to suggest that genetic and epigenetic mechanisms contribute to these immune responses. Initial investigations into the biology of non-T2 immune responses have identified upregulation of genes in the CDC42 pathway. CDC42 is a RhoGTPase that plays a key role in Th cell physiology, including preferential naïve Th cell differentiation to Th1 cells, as well as cytokine production and exocytosis. These novel pathways are promising findings to direct targeted therapy development for obesity-related asthma to address the disease burden.

Combined unsupervised-supervised machine learning for phenotyping complex diseases with its application to obstructive sleep apnea

Unsupervised clustering models have been widely used for multimetric phenotyping of complex and heterogeneous diseases such as diabetes and obstructive sleep apnea (OSA) to more precisely characterize the disease beyond simplistic conventional diagnosis standards. However, the number of clusters and key phenotypic features have been subjectively selected, reducing the reliability of the phenotyping results. Here, to minimize such subjective decisions for highly confident phenotyping, we develop a multimetric phenotyping framework by combining supervised and unsupervised machine learning. This clusters 2277 OSA patients to six phenotypes based on their multidimensional polysomnography (PSG) data. Importantly, these new phenotypes show statistically different comorbidity development for OSA-related cardio-neuro-metabolic diseases, unlike the conventional single-metric apnea-hypopnea index-based phenotypes. Furthermore, the key features of highly comorbid phenotypes were identified through supervised learning rather than subjective choice. These results can also be used to automatically phenotype new patients and predict their comorbidity risks solely based on their PSG data. The phenotyping framework based on the combination of unsupervised and supervised machine learning methods can also be applied to other complex, heterogeneous diseases for phenotyping patients and identifying important features for high-risk phenotypes.

Higher body mass index is associated with increased lung stiffness and less airway obstruction in individuals with asthma and fixed airflow obstruction

Persistent or fixed airflow obstruction (FAO) is prevalent in up to 60% of patients with severe asthma [1] and is associated with older age, more rapid decline in lung function and increased symptoms [1–3]. The underlying mechanisms of FAO in asthma are unknown, but growing evidence suggests that parenchymal changes resulting in loss of elastic recoil and decreased lung stiffness (i.e. increased lung compliance) contribute to FAO [2, 4]. In a recent study of older asthma patients with FAO, decreased lung stiffness was the sole predictor of more severe airflow obstruction, as measured by reduced forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ratio [2].

Higher body mass index (BMI) is associated with less severe airway obstruction in older asthma patients with fixed airflow obstruction. This is potentially mediated through BMI-related mechanisms that increase lung stiffness (i.e. reduce lung compliance).https://bit.ly/3jBwCNy

Central airway collapse is related to obesity independent of asthma phenotype

BACKGROUND AND OBJECTIVE

Late-onset non-allergic asthma in obesity is characterized by an abnormally compliant, collapsible lung periphery; it is not known whether this abnormality exists in proximal airways. We sought to compare collapsibility of central airways between lean and obese individuals with and without asthma.

METHODS

A cross-sectional study comparing luminal area and shape (circularity) of the trachea, left mainstem bronchus, right bronchus intermedius and right inferior lobar bronchus at RV and TLC by CT was conducted.

RESULTS

In 11 lean controls (BMI: 22.4 (21.5, 23.8) kg/m² ), 10 lean individuals with asthma (23.6 (22.0, 24.8) kg/m² ), 10 obese controls (45.5 (40.3, 48.5) kg/m² ) and 21 obese individuals with asthma (39.2 (35.8, 42.9) kg/m² ), lumen area and circularity increased significantly with an increase in lung volume from RV to TLC for all four airways (P < 0.05 for all). Changes in area and circularity with lung volume were similar in obese individuals with and without asthma, and both obese groups had severe airway collapse at RV. In multivariate analysis, change in lumen area was related to BMI and change in circularity to waist circumference, but neither was related to asthma diagnosis.

CONCLUSION

Excessive collapse of the central airways is related to obesity, and occurs in both obese controls and obese asthma. Increased airway collapse could contribute to ventilation abnormalities in obese individuals particularly at lower lung volumes, and complicate asthma in obese individuals.

Heterogeneity of Childhood Asthma in Korea: Cluster Analysis of the Korean Childhood Asthma Study Cohort

PURPOSE

Asthma is a heterogeneous airway disease occurring in children, and it has various clinical phenotypes. A clear differentiation of the clinical phenotypes can provide better asthma management and prediction of asthma prognosis. Little is currently known about asthma phenotypes in Korean children. This study was designed to identify asthma phenotypes in school-aged Korean children.

METHODS

This study enrolled 674 children with physician-diagnosed asthma from the Korean childhood Asthma Study (KAS) cohort. The physicians verified the relevant histories of asthma and comorbid diseases, as well as airway lability and hyper-responsiveness from the results of pulmonary function tests and bronchial provocation tests. Questionnaires regarding the participants' baseline characteristics, their environment and self-rating of asthma control were collected at the time of enrollment. Laboratory tests were performed to assess allergy and airway inflammation. Children with asthma were classified by hierarchical cluster analysis.

RESULTS

Of the 674 patients enrolled from the KAS cohort, 447 were included in the cluster analysis. Cluster analysis of these 447 children revealed 4 asthma phenotypes: cluster 1 (n = 216, 48.3%) which was characterized by male-dominant atopic asthma; cluster 2 (n = 79, 17.7%) which was characterized by early-onset atopic asthma with atopic dermatitis; cluster 3 (n = 47, 10.5%) which was characterized by puberty-onset, female-dominant atopic asthma with the low lung function; and cluster 4 (n = 105, 23.5%) which was characterized by early-onset, non-atopic dominant asthma.

CONCLUSIONS

The asthma phenotypes among Korean children can be classified into 4 distinct clusters. Long-term follow-up with these phenotypes will be needed to define their prognosis and response to treatment.