Historically, a wide variety of criteria have been used inconsistently to define severe asthma. However, our understanding of the range of characteristics associated with severe asthma has greatly evolved as a result of large-scale studies.1
A joint committee of the European Respiratory Society and American Thoracic Society (ERS/ATS) defined severe asthma as:
Asthma that requires use of high-dose inhaled corticosteroids (ICS) plus a long-acting beta2-agonist (LABA) or leukotriene modifier/theophylline for the previous year or systemic corticosteroids for ≥50% of the previous year (GINA steps 4-5 therapy) to prevent it from becoming uncontrolled, or that remains uncontrolled despite this therapy.2
Patients meeting the criteria below are defined as having severe asthma, which may be further classified as “controlled” or “uncontrolled”2:
Asthma is a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness, and an underlying inflammation. The interaction of these features of asthma determines the clinical manifestations and severity of asthma and the response to treatment.3,4
The illustration below demonstrates the interplay and interaction between airway inflammation, clinical symptoms, and pathophysiology of asthma.4
Reprinted from National Heart, Lung, and Blood Institute Guidelines for the Diagnosis and Management of Asthma. EPR 3, section 2, p13, Figure 2, 2007.
Common symptoms of asthma include5:
References: 1. Wenzel S. Severe asthma: from characteristics to phenotypes to endotypes. Clin Exp Allergy. 2012;42(5):650-658. 2. Chung KF, Wenzel SE, Brozek JL, et al. International ERS/ATS guidelines on definition, evaluation and treatment of severe asthma. Eur Respir J. 2014;43(2):343-373. 3. Global Initiative for Asthma. Global strategy for asthma management and prevention, 2017. www.ginasthma.org. Accessed June 22, 2017. 4. National Institutes of Health. Section 2, Definition, pathophysiology and pathogenesis of asthma, and natural history of asthma. In: Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma. Bethesda, MD: National Heart, Lung, and Blood Institute (US); 2007. www.ncbi.nlm.nih.gov/books/NBK7223/. Accessed June 22, 2017. 5. What are the symptoms of asthma? Asthma and Allergy Foundation website. www.aafa.org/page/asthma-symptoms.aspx. Accessed June 22, 2017. 6. King ME, Mannino DM, Holguin F. Risk factors for asthma incidence, A review of recent prospective evidence. Panminerva Med. 2004;46:97-111. 7. Kumar RK, Jeffery PK. Pathology of asthma. In: Adkinson Jr NF, Bochner BS, Burks AW, et al, eds. Middleton’s Allergy Principles and Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:986-999.