In this first of a 2-part podcast series on uncontrolled asthma, Samuel Louie, MD, University of California, Davis, discusses current methods to recognize features of uncontrolled asthma and asthma phenotypes, particularly severe asthma. Claim your credit at pce.is/ua.
Asthma is now recognized as a heterogeneous, multidimensional disease that involves numerous pathophysiologic factors, including bronchiolar inflammation with airway constriction and resistance. The identification of distinct patient populations (phenotypes/endotypes) is increasingly being recognized as an important strategy for optimizing the management of patients with asthma. Asthma phenotype is based on clinical symptoms such as respiratory function, onset age, and blood biochemical examination values.
Clinical studies have shown that asthma phenotypes have specific patterns of inflammation that require different treatment approaches. For example, eosinophilic asthma is characterized by airway and systemic markers of eosinophilia, subepithelial fibrosis, and corticosteroid responsiveness, whereas non-eosinophilic asthma is characterized by the absence of eosinophilia and subepithelial fibrosis, as well as poor responsiveness to corticosteroids. In addition to high immunoglobulin (Ig) E levels in up to 60% of patients, asthma is characterized by tissue eosinophilia, which is mediated in part by interleukin (IL)-5. Because eosinophils produce inflammatory proteins that lead to tissue damage, the eosinophilic phenotype of asthma is associated with greater symptom severity, increased risk of exacerbation, and decreased lung function. The GINA guidelines recommend that asthma should be classified by phenotype, especially when it becomes difficult to treat or refractory to treatment.
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Contributors:
Lawrence Herman, DMSc, MPA, PA-C
Adjunct Faculty
Doctor of Medical Science Program
University of Lynchburg School of PA Medicine
Lynchburg, Virginia
President
Palantir Healthcare, LLC
Boiling Springs, South Carolina
Samuel Louie, MD
Professor Emeritus
Division of Pulmonary and Critical Care Medicine
University of California, Davis
Davis, California