Risk factors for frequent severe exacerbations in late-onset eosinophilic asthma

Phenotype overlap in the natural history of asthma

The heterogeneity of asthma makes it challenging to unravel the pathophysiologic mechanisms of the disease. Despite the wealth of research identifying diverse phenotypes, many gaps still remain in our knowledge of the disease's complexity. A crucial aspect is the impact of airborne factors over a lifetime, which often results in a complex overlap of phenotypes associated with type 2 (T2), non-T2 and mixed inflammation. Evidence now shows overlaps between the phenotypes associated with T2, non-T2 and mixed T2/non-T2 inflammation. These interconnections could be induced by different determinants such as recurrent infections, environmental factors, T-helper plasticity and comorbidities, collectively resulting in a complex network of distinct pathways generally considered as mutually exclusive. In this scenario, we need to abandon the concept of asthma as a disease characterised by distinct traits grouped into static segregated categories. It is now evident that there are multiple interplays between the various physiologic, cellular and molecular features of asthma, and the overlap of phenotypes cannot be ignored.

Mild asthma: Lessons learned and remaining questions

Patients living with mild disease represent the largest proportion of asthma patients. There are significant challenges in proposing a definition that would best describe these patients, while also accurately identifying at-risk individuals. Current literature suggests considerable inflammatory and clinical heterogeneity within this group. Research has shown that these patients are at risk of poor control, exacerbations, lung function decline, and death. Despite conflicting data on its prevalence, eosinophilic inflammation appears to be a predictor of poorer outcomes in mild asthma. There is an immediate need to better understand phenotypic clusters in mild asthma. It is also important to understand factors that influence disease progression and remission, as it is evident that both vary in mild asthma. Guided by robust literature that supports inhaled corticosteroid-based strategies over short-acting beta-agonist (SABA) reliant regimens, the management of these patients has evolved considerably. Unfortunately, SABA use remains high in clinical practice despite strong advocacy from the Global Initiative for Asthma. Future mild asthma research should explore the role of biomarkers, develop prediction tools based on composite risk scores, and explore targeted therapies at least for at-risk individuals.

Asthma Exacerbations: Patient Features and Potential Long-Term Implications

Asthma exacerbations occur in the context of a complex interplay between external exposures and host factors. Respiratory tract viral infections, in particular rhinovirus, are dominant initiators of exacerbations, with allergens and other inhalation exposures as additional key contributors. The presence of underlying type II inflammation, with associated biomarker elevations, is a major driver of exacerbation risk and mechanism, as evidenced by the consistent reduction of exacerbations seen with biologics targeting these pathways. Several genetic polymorphisms are associated with exacerbations, and while they may individually have small effects, they are cumulatively important and magnified by environmental exposures. A history of exacerbations predicts future exacerbations with potentially negative implications on long-term lung health.

Small Airways: The “Silent Zone” of 2021 GINA Report?

Asthma is a chronic disease, affecting approximately 350 million people worldwide. Inflammation and remodeling in asthma involve the large airways, and it is now widely accepted that the small airways (those with an internal diameter <2 mm) are involved in the pathogenesis of asthma and are the major determinant of airflow obstruction in this disease. From a clinical perspective, small airways dysfunction (SAD) is associated with more severe bronchial hyperresponsiveness, worse asthma control and more exacerbations. Unlike the GOLD guidelines which, in their definition, identify COPD as a disease of the small airways, the Global Initiative for Asthma (GINA) guidelines do not refer to the prevalence and role of SAD in asthmatic patients. This decision seems surprising, given the growing body of compelling evidence accumulating pointing out the high prevalence of SAD in asthmatic patients and the importance of SAD in poor asthma control. Furthermore, and remarkably, SAD appears to possess the characteristics of a treatable pulmonary trait, making it certainly appealing for asthma control optimization and exacerbation rate reduction. In this mini-review article, we address the most recent evidence on the role of SAD on asthma control and critically review the possible inclusion of SAD among treatable pulmonary traits in international guidelines on asthma.

Revisiting Mild Asthma: Current Knowledge and Future Needs

Asthma is a common chronic airways disease with significant impact on patients, caregivers, and the health-care system. Although most research and novel interventions mainly have focused on patients with uncontrolled severe asthma, most patients with asthma have mild disease. Epidemiologic studies suggest that many patients with mild asthma report frequent exacerbations of the disease and uncontrolled symptoms. However, despite its impact, mild asthma does not have either a uniformly agreed on definition for or a consensus on its clinical and pathophysiologic progression. More recently, the approach to treatment of patients with mild asthma has undergone significant changes primarily based on emerging evidence that airway inflammation in this population is important. This led to clinical research studies that explored the efficacy of as-needed inhaled corticosteroids along with the rescue medications that traditionally have been the mainstay of treatment. Despite some advancement in the field in recent years, many controversies and unmet needs remain. In this review, we examine the current understanding of the pathophysiologic features and management of mild asthma. In addition, we outline unmet needs for future research. We conclude that mild asthma contributes significantly to the morbidity and mortality of asthma and should be the focus of future research.

Patient characteristics, biomarkers, and exacerbation risk in severe, uncontrolled asthma

BACKGROUND

Greater precision in asthma exacerbation risk prediction may improve outcomes. We sought to identify clinical characteristics and biomarkers associated with elevated exacerbation risk in patients with severe, uncontrolled asthma.

METHODS

Data were pooled from seven similarly designed Phase II and III randomized controlled clinical trials of biologic therapies for the treatment of severe, uncontrolled asthma that enrolled comparable patient populations. Annualized asthma exacerbation rates (AAERs) for patients randomized to placebo were assessed by baseline clinical characteristics and by biomarker concentrations at baseline and over the study duration.

RESULTS

The AAER for the 2016 patients in the combined placebo group was 0.91 (95% CI 0.84‒0.98). Baseline characteristics associated with greater AAER were frequent or severe exacerbations within the prior 12 months, nasal polyposis, maintenance oral corticosteroid use, Asian race, and Asian or Western European region. AAER increased with baseline blood eosinophil counts and fractional exhaled nitric oxide (FeNO) concentration, with the greatest AAER occurring for patients with eosinophils ≥300 cells·μL^-1 and FeNO ≥50 ppb. No relationship was observed between baseline serum immunoglobulin E concentration and AAER. Combining type 2 inflammation criteria for eosinophils and FeNO had greater prognostic value than either biomarker alone. Persistent eosinophil and FeNO elevations throughout the study period were associated with greater AAER.

CONCLUSIONS

Exacerbation history, maintenance corticosteroid use, nasal polyposis, Asian race, geographic region, and elevations in blood eosinophil counts and FeNO concentrations (particularly when combined and/or persistently achieving type 2 inflammation criteria) were associated with increased exacerbation risk in patients with severe, uncontrolled asthma.

Factors Associated with Frequent Exacerbations in the UK Severe Asthma Registry

BACKGROUND

Frequent exacerbations are an important cause of morbidity in patients with severe asthma.

OBJECTIVE

Our aim was to identify factors associated with frequent exacerbations in a large well-characterized severe asthma population and determine whether factors differed in patients treated with and without maintenance oral corticosteroids (OCS).

METHODS

Adults with severe asthma from specialized asthma centers across the United Kingdom were recruited to the UK Severe Asthma Registry. Demography, comorbidities and physiological measurements were collected. We conducted univariable and multivariable logistic regression analyses to identify factors associated with frequent exacerbations, defined as 3 or more exacerbations treated with high-dose systemic corticosteroids in the past year.

RESULTS

Of 1,592 patients with severe asthma from the UK Severe Asthma Registry, 1,137 (71%) were frequent exacerbators and 833 (52%) were on maintenance OCS. The frequent exacerbators were more likely to be ex-smokers, have gastroesophageal reflux disease, higher Asthma Control Questionnaire-6 (ACQ-6) score, and higher blood eosinophilia. Multivariable regression analyses showed ACQ-6 score greater than 1.5 (odds ratio [OR] 4.25; P < .001), past smoking history (OR 1.55; P = .024), and fractional exhaled nitric oxide greater than 50ppb (OR 1.54; P = .044) were independently associated with frequent exacerbations. Past smoking history correlated with frequent exacerbations only in patients on maintenance OCS (OR 2.25; P = .004), whereas ACQ-6 score greater than 1.5 was independently associated with frequent exacerbations in those treated with and without maintenance OCS (OR 2.74; P = .017 and OR 6.42; P < .001, respectively).

CONCLUSIONS

Several factors were associated with frequent exacerbations in a large UK severe asthma registry population. High ACQ-6 score had the strongest association with frequent exacerbations irrespective of maintenance OCS status.

Clinical and Inflammatory Features of Exacerbation-Prone Asthma: A Cross-Sectional Study Using Multidimensional Assessment

BACKGROUND

Reducing asthma exacerbations is a major target of current clinical guidelines, but identifying features of exacerbation-prone asthma (EPA) using multidimensional assessment (MDA) is lacking.

OBJECTIVE

To systemically explore the clinical and inflammatory features of adults with EPA in a Chinese population.

METHODS

We designed a cross-sectional study using the Severe Asthma Web-based Database from the Australasian Severe Asthma Network (ASAN). Eligible Chinese adults with asthma (n = 546) were assessed using MDA. We stratified patients based on exacerbation frequency: none, few (1 or 2), and exacerbation prone (≥3). Univariate and multivariable negative binomial regression analyses were performed to investigate features associated with the frequency of exacerbations.

RESULTS

Of 546 participants, 61.9% had no exacerbations (n = 338), 29.6% had few exacerbations (n = 162), and 8.4% were exacerbation prone (n = 46) within the preceding year. EPA patients were characterized by elevated blood and sputum eosinophils but less atopy, with more controller therapies but worse asthma control and quality of life (all p < 0.05). In multivariable models, blood and sputum eosinophils (adjusted rate ratio = 2.23, 95% confidence interval = [1.26, 3.84] and 1.67 [1.27, 2.21], respectively), FEV1 (0.90 [0.84, 0.96]), bronchodilator responsiveness (1.16 [1.05, 1.27]), COPD (2.22 [1.41, 3.51]), bronchiectasis (2.87 [1.69, 4.89]), anxiety (2.56 [1.10, 5.95]), and depression (1.94 [1.20, 3.13]) were found. Further, upper respiratory tract infection (1.83 [1.32, 2.54]) and food allergy (1.67 [1.23, 2.25]) were at high risk of asthma symptom triggers.

CONCLUSION

EPA is a clinically recognizable phenotype associated with several recognizable traits that could be addressed by targeted treatment.

Exacerbation-Prone Asthma

Patients who are prone to exacerbations of asthma experience significant costs in terms of missed work and school, acute care visits, and hospitalizations. Exacerbations are largely driven by environmental exposures including pollutants, stress, and viral and bacterial pathogens. These exposures are most likely to induce acute severe "asthma attacks" in high-risk patients. These personal risk factors for exacerbations can vary with the phenotype of asthma and age of the patient. In children, allergic sensitization is a strong risk factor, especially for those children who develop sensitization early in life. Airway inflammation is an important risk factor, and biomarkers are under evaluation for utility in detecting eosinophilic and type 2 inflammation and neutrophilic inflammation as indicators of risk for recurrent exacerbations. Insights into inflammatory mechanisms have led to new approaches to prevent exacerbations using mAb-based biologics that target specific type 2 pathways. Challenges remain in developing an evidence base to support precision interventions with these effective yet expensive therapies, and in determining whether these treatments will be safe and effective in young children. Unfortunately, there has been less progress in developing treatments for acute exacerbations. Hopefully, greater understanding of mechanisms relating airway viruses, bacteria, mucin production, and neutrophilic inflammatory responses will lead to additional treatment options for patients experiencing acute exacerbations.

Asthma exacerbation related to viral infections: An up to date summary

Asthma exacerbation can be a major life threatening event. Viruses have been pinned as the cause behind the vast majority of these exacerbations. The purpose of this short review is to explore the mechanisms behind these exacerbations, focusing mostly on viral infections as triggers. We will also be discussing the phenotypes prone to asthma exacerbation, the pathophysiology of viral induced asthma and ventilation patterns of asthmatic lungs. This manuscript will assist primary care physicians in delineating the proper pathophysiology of the disease as well as the management.

ERS/EAACI statement on severe exacerbations in asthma in adults: facts, priorities and key research questions

Despite the use of effective medications to control asthma, severe exacerbations in asthma are still a major health risk and require urgent action on the part of the patient and physician to prevent serious outcomes such as hospitalisation or death. Moreover, severe exacerbations are associated with substantial healthcare costs and psychological burden, including anxiety and fear for patients and their families. The European Academy of Allergy and Clinical Immunology (EAACI) and the European Respiratory Society (ERS) set up a task force to search for a clear definition of severe exacerbations, and to also define research questions and priorities. The statement includes comments from patients who were members of the task force.

Exacerbation-prone asthma in the context of race and ancestry in Asthma Clinical Research Network trials

BACKGROUND

Minority groups of African descent experience disproportionately greater asthma morbidity compared with other racial groups, suggesting that genetic variation from a common ancestry could influence exacerbation risk.

OBJECTIVE

We evaluated clinical trial measures in the context of self-reported race and genetic ancestry to identify risk factors for asthma exacerbations.

METHODS

One thousand eight hundred forty multiethnic subjects from 12 Asthma Clinical Research Network and AsthmaNet trials were analyzed for incident asthma exacerbations with Poisson regression models that included clinical measures, self-reported race (black, non-Hispanic white, and other), and estimates of global genetic African ancestry in a subgroup (n = 760).

RESULTS

Twenty-four percent of 1840 subjects self-identified as black. Black and white subjects had common risk factors for exacerbations, including a history of 2 or more exacerbations in the previous year and FEV₁ percent predicted values, whereas chronic sinusitis, allergic rhinitis, and gastroesophageal reflux disease were only associated with increased exacerbation risk in black subjects. In the combined multiethnic cohort, neither race (P = .30) nor percentage of genetic African ancestry as a continuous variable associated with exacerbation risk (adjusted rate ratio [RR], 1.26 [95% CI, 0.94-1.70; P = .13]; RR per 1-SD change [32% ancestry], 0.97 [95% CI, 0.78-1.19; P = .74]). However, in 161 black subjects with genetic data, those with African ancestry greater than the median (≥82%) had a significantly greater risk of exacerbation (RR, 3.06 [95% CI, 1.09-8.6; P = .03]).

CONCLUSION

Black subjects have unique risk factors for asthma exacerbations, of which global African genetic ancestry had the strongest effect.

Role of sputum biomarkers in the management of asthma

PURPOSE OF REVIEW

Airway inflammation is considered to be a cardinal feature of asthma. However, the type of airway inflammation is heterogeneous and airway inflammation may even be absent. Biomarkers may help to identify the inflammatory phenotype or endotype, especially now the time has come that targeted therapies enter daily practice.

RECENT FINDINGS

Sputum biomarkers have increased our insights into the different inflammatory asthma phenotypes, their response to treatment and their association with progression of disease. New endotypes of type 2 driven inflammation were identified using a multidimensional approach. A specific mast cell subtype has been linked with type 2 driven inflammation and response to inhaled corticosteroids. Advances have been made with regard to sputum cytokine analysis and might also help to guide future treatment of severe asthma.

SUMMARY

Identifying the target population for biological therapies will not be possible without the use of biomarkers. Optimized, easy-to-apply, automated methods for sputum analysis (cellular content or soluble markers) need to be developed for implementation of sputum biomarkers in daily clinical practice.

Late-onset asthma: current perspectives

Because the pathophysiology of asthma has diverse characteristics, to manage the disease effectively, it is important for clinicians to distinguish among the clinical phenotypes. Among them, adult-onset asthma, that is, late-onset asthma (LOA), is increasing because of the aging of the population. The phenotype of LOA is largely divided into two types according to the presence or absence of eosinophilic inflammation, T-helper (Th)2- and non-Th2-associated LOA. Especially in Th2 LOA related to rhinosinusitis, as pulmonary function at onset is poor and asthma exacerbations occur frequently, it is important to detect this phenotype in the early phase by using a biomarker of Th2-type inflammation such as fractional exhaled nitric oxide (FENO). As non-Th2-LOA is often resistant to corticosteroids, this phenotype often requires another treatment strategy such as macrolide, diet, or smoking cessation. We often struggle with the management of LOA patients due to a lack of evidence; therefore, the elucidation of the mechanism of LOA contributes to increased efficiency of diagnosis and treatment of LOA. Age-related immune system and structural changes are thought to be associated with the pathophysiology of LOA. In the former case, changes in inflammatory cell function such as variations in the innate immune response and acquisition of autoimmunity or upregulation of oxidative stress are thought to be involved in the mechanism. Meanwhile, the latter can also become triggers or exacerbating factors of LOA via enhancement of airway hyperresponsiveness, decline in lung function, increased air trapping, and reduction in chest wall compliance. Therefore, appropriate individualized management in LOA may be possible through precisely assessing the pathophysiology based on age-related functional changes, including the immune and structural system.

Effect of obesity on sinonasal disease in asthma

OBJECTIVE

Sinonasal disease can contribute to poor asthma control. There are reports that link obesity with an increased prevalence of sinonasal disease, but no studies evaluating the severity of sinonasal disease in obese asthmatics, and how this impacts asthma control. The purpose of the current study was to determine if obesity is associated with increased severity of sinonasal disease, and/or affects response to nasal corticosteroid treatment in asthma.

METHODS

This study included 236 adults participating in a 24-week randomized, double-masked, placebo-controlled study of nasal mometasone for the treatment of poorly controlled asthma. Sinonasal disease severity was assessed using validated questionnaires, and compared in participants of differing BMIs. Eosinophilic inflammation was assessed using markers in nasal lavage, serum and exhaled nitric oxide. Response to treatment was compared in different BMI groups.

RESULTS

Obesity had no effect on the severity of sinonasal disease symptoms in asthmatics (Sino-Nasal Outcome Test 22 (SNOT 22) score [mean ± SD] 35.4 ± 18.5, 40.2 ± 22.8, and 39.1 ± 21.7, p = 0.43, in lean, overweight and obese participants), nor on nasal, bronchial or systemic markers of allergic inflammation. Nasal steroids had some limited effects on symptoms, lung function and inflammatory markers in lean participants, but no detectable effect was found in obese patients.

CONCLUSIONS

Obesity does not affect severity of sinonasal disease in patients with asthma; the association of sinonasal disease symptoms with increased asthma severity and markers of Type 2 inflammation are consistent across all BMI groups. The response of obese patients to nasal corticosteroids requires further study.

Identification of phenotypic clusters of nonsteroidal anti-inflammatory drugs exacerbated respiratory disease

BACKGROUND

Clinical presentation of nonsteroidal anti-inflammatory drugs exacerbated respiratory disease (NERD) is found to be heterogeneous. This study classified phenotypic clusters to determine NERD subtypes.

METHODS

We performed two-step cluster analysis using urticaria, chronic rhinosinusitis (CRS), and atopy, in a NERD cohort comprising 302 patients. Asthma exacerbation was defined as receiving at least one burst of intravenous steroid treatment and/or at least two bursts of oral steroid use (≥ 45 mg/3 days) per year. The possession rate of anti-asthmatic medications was estimated during the follow-up period.

RESULTS

There were four subtypes: subtype 1 (NERD with CRS/atopy and no urticaria), subtype 2 (NERD with CRS and no urticaria/atopy), subtype 3 (NERD without CRS/urticaria), and subtype 4 (NERD with urticaria). Significant differences were found between the four subtypes in the female proportion, baseline FEV1%, serum total IgE level, and sputum/peripheral eosinophil count. A higher frequency of asthma exacerbations was noted in subtype 1 compared to subtype 3. The possession rates of medium- to high-dose inhaled corticosteroids/long-acting beta₂ -agonists showed significant differences among the four subtypes. Metabolomic analysis showed that the four subtypes of NERD had a higher serum leukotriene E4 (LTE4) level than those with aspirin-tolerant asthma. The patients with subtypes 1 and 3 had a higher urine LTE4 level than those with subtype 2.

CONCLUSION

We found four distinct subtypes with different clinical/biochemical findings and asthma exacerbations in a NERD cohort. These findings suggest that stratified strategies by applying subtype classification may help achieve better outcomes in the management of NERD.

Diagnosis and investigation in the severe asthma clinic

Severe asthma is recognised as an important and emerging area of unmet need in asthma. The assessment of severe asthma should include three steps; (1) determining the diagnosis of asthma, including verification that the disease is severe asthma, (2) assessing comorbidities and contributing factors that will impact on clinical severity, as well as (3) assessing asthma phenotypes. These steps recognize the importance of heterogeneity in asthma as a key factor that determines the disease course and increasingly the choice of successful therapy. This assessment should be undertaken systematically and is best done by an expert multidisciplinary team. Here, we will outline the important aspects that should be included in the clinical assessment of the patient in the severe asthma clinic, including diagnosis, clinical history, the assessment of important comorbidities and the key investigations needed to support them.