Phenotyping of Severe Asthma in the Era of Broad-acting Anti-asthma Biologics

Severe asthma is associated with significant morbidity and mortality despite maximal use of inhaled corticosteroids and additional controller medications, and has a high economic burden. Biologic therapies are recommended for the management of severe, uncontrolled asthma to help prevent exacerbations and to improve symptoms and health-related quality of life. Effective management of severe asthma requires consideration of clinical heterogeneity that is driven by varying clinical and inflammatory phenotypes, which are reflective of distinct underlying disease mechanisms. Phenotyping patients using a combination of clinical characteristics such as age of onset or comorbidities and biomarker profiles, including blood eosinophil counts, and levels of fractional exhaled nitric oxide and serum total immunoglobulin E, is important for the differential diagnosis of asthma. Additionally, phenotyping is beneficial for risk assessment, selection of treatment, and monitoring of treatment response in patients with asthma. This review describes the clinical and inflammatory phenotypes of asthma, provides an overview of biomarkers routinely used in clinical practice and those that have recently been explored for phenotyping, and aims to assess the value of phenotyping in severe asthma management in the current era of biologics.