Severe or therapy-resistant asthma is increasingly recognised as a major unmet need. A Task Force, supported by the European Respiratory Society and American Thoracic Society, reviewed the definition and provided recommendations and guidelines on the evaluation and treatment of severe asthma in children and adults. A literature review was performed, followed by discussion by an expert committee according to the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach for development of specific clinical recommendations. When the diagnosis of asthma is confirmed and comorbidities addressed, severe asthma is defined as asthma that requires treatment with high dose inhaled corticosteroids plus a second controller and/or systemic corticosteroids to prevent it from becoming “uncontrolled” or that remains “uncontrolled” despite this therapy. Severe asthma is a heterogeneous condition consisting of phenotypes such as eosinophilic asthma. Specific recommendations on the use of sputum eosinophil count and exhaled nitric oxide to guide therapy, as well as treatment with anti-IgE antibody, methotrexate, macrolide antibiotics, antifungal agents and bronchial thermoplasty are provided. Coordinated research efforts for improved phenotyping will provide safe and effective biomarker-driven approaches to severe asthma therapy.

/pdf/international-ers-ats-guidelines-on-definition-evaluation-sedelwbk4v.pdf

International ERS/ATS guidelines on definition, evaluation and treatment of severe asthma

Although asthma has been considered as a single disease for years, recent studies have increasingly focused on its heterogeneity. The characterization of this heterogeneity has promoted the concept that asthma consists of multiple phenotypes or consistent groupings of characteristics. Asthma phenotypes were initially focused on combinations of clinical characteristics, but they are now evolving to link biology to phenotype, often through a statistically based process. Ongoing studies of large-scale, molecularly and genetically focused and extensively clinically characterized cohorts of asthma should enhance our ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to asthma therapy.

/pdf/asthma-phenotypes-the-evolution-from-clinical-to-molecular-1a6ydbpfb2.pdf

Asthma phenotypes: the evolution from clinical to molecular approaches

Rationale: The Severe Asthma Research Program cohort includes subjects with persistent asthma who have undergone detailed phenotypic characterization. Previous univariate methods compared features of mild, moderate, and severe asthma.Objectives: To identify novel asthma phenotypes using an unsupervised hierarchical cluster analysis.Methods: Reduction of the initial 628 variables to 34 core variables was achieved by elimination of redundant data and transformation of categorical variables into ranked ordinal composite variables. Cluster analysis was performed on 726 subjects.Measurements and Main Results: Five groups were identified. Subjects in Cluster 1 (n = 110) have early onset atopic asthma with normal lung function treated with two or fewer controller medications (82%) and minimal health care utilization. Cluster 2 (n = 321) consists of subjects with early-onset atopic asthma and preserved lung function but increased medication requirements (29% on three or more medications) and health care utilizati...

Identification of Asthma Phenotypes Using Cluster Analysis in the Severe Asthma Research Program

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140673602116795.pdf

Asthma exacerbations and sputum eosinophil counts: a randomised controlled trial.

Rationale: T-helper type 2 (Th2) inflammation, mediated by IL-4, IL-5, and IL-13, is considered the central molecular mechanism underlying asthma, and Th2 cytokines are emerging therapeutic targets. However, clinical studies increasingly suggest that asthma is heterogeneous.Objectives: To determine whether this clinical heterogeneity reflects heterogeneity in underlying molecular mechanisms related to Th2 inflammation.Methods: Using microarray and polymerase chain reaction analyses of airway epithelial brushings from 42 patients with mild-to-moderate asthma and 28 healthy control subjects, we classified subjects with asthma based on high or low expression of IL-13–inducible genes. We then validated this classification and investigated its clinical implications through analyses of cytokine expression in bronchial biopsies, markers of inflammation and remodeling, responsiveness to inhaled corticosteroids, and reproducibility on repeat examination.Measurements and Main Results: Gene expression analyses ident...

T-helper Type 2–driven Inflammation Defines Major Subphenotypes of Asthma

The mechanisms associated with the development of severe, corticosteroid (CS)-dependent asthma are poorly understood, but likely heterogenous. It was hypothesized that severe asthma could be divided pathologically into two inflammatory groups based on the presence or absence of eosinophils, and that the inflammatory subtype would be associated with distinct structural, physiologic, and clinical characteristics. Thirty-four severe, refractory CS-dependent asthmatics were evaluated with endobronchial biopsy, pulmonary function, allergy testing, and clinical history. Milder asthmatic and normal control subjects were also evaluated. Tissue cell types and subbasement membrane (SBM) thickness were evaluated immunohistochemically. Fourteen severe asthmatics [eosinophil ( 2 )] had nearly absent eosinophils ( , 2 SD from the normal mean). The remaining 20 severe asthmatics were categorized as eosinophil ( 1 ). Eosinophil ( 1 ) severe asthmatics had associated increases (p , 0.05) in lymphocytes (CD3 1 , CD4 1 , CD8 1 ), mast cells, and macrophages. Neutrophils were increased in severe asthmatics and not different between the groups. The SBM was significantly thicker in eosinophil ( 1 ) severe asthmatics than eosinophil ( 2 ) severe asthmatics and correlated with eosinophil numbers (r 5 0.50). Despite the absence of eosinophils and the thinner SBM, the FEV 1 was marginally lower in eosinophil ( 2 ) asthmatics (p 5 0.05) with no difference in bronchodilator response. The eosinophil ( 1 ) group (with a thicker SBM) had more intubations than the eosinophil ( 2 ) group (p 5 0.0004). Interestingly, this group also had a decreased FVC/slow vital capacity (SVC). These results suggest that two distinct pathologic, physiologic, and clinical subtypes of severe asthma exist, with implications for further research and treatment. Wenzel SE, Schwartz LB, Langmack EL, Halliday JL, Trudeau JB, Gibbs RL, Chu HW. Evidence that severe asthma can be divided pathologically into two inflammatory subtypes with distinct physiologic and clinical characteristics. AM J RESPIR CRIT CARE MED 1999;160:1001‐1008.

https://www.atsjournals.org/doi/pdf/10.1164/ajrccm.160.3.9812110

Evidence That Severe Asthma Can Be Divided Pathologically into Two Inflammatory Subtypes with Distinct Physiologic and Clinical Characteristics

Chronic airway inflammation and remodeling, including fibrosis, have been proposed as important contributors to asthma pathophysiology. Previous studies of airway fibrosis have been performed mainly in mild and moderate asthmatics at the subepithelial "basement membrane" (SBM) level. The current study was designed to evaluate the large airway SBM thickness and submucosal collagen deposition, as measured by three different collagen staining methods, in endobronchial biopsies from 17 severe, nine moderate, and seven mild asthmatics, as well as eight normal control subjects. Tissue eosinophils and transforming growth factor-beta (TGF-beta) immunoreactivity were also examined. There were no statistically significant differences in the SBM thickness, submucosal collagen deposition, eosinophil numbers, or TGF-beta positive cells among the three groups of asthmatics and the normal control subjects. It was only when examining all asthmatics (n = 33) together, that a modestly thickened SBM (p = 0.04), as evaluated by collagen type III immunostaining, was observed as compared with normal control subjects. Despite this difference, no significant differences were found in the amount of submucosal collagen deposition and the number of eosinophils or TGF-beta expressing cells when comparing total asthmatics and normal control subjects. Additionally, no significant correlations were found between collagen deposition and eosinophil count, TGF-beta expression level, FEV1, or duration of asthma. These results suggest that although increased collagen deposition in the SBM at the large airway level is a characteristic of asthma, it may not explain the differences in severity of asthma.

https://www.atsjournals.org/doi/pdf/10.1164/ajrccm.158.6.9712073

Janet L. Halliday

Papers

Evidence That Severe Asthma Can Be Divided Pathologically into Two Inflammatory Subtypes with Distinct Physiologic and Clinical Characteristics

Collagen Deposition in Large Airways May Not Differentiate Severe Asthma from Milder Forms of the Disease