Recognition and management of severe asthma: A Canadian Thoracic Society position statement

RATIONALE: While severe asthma affects approximately 5% of all individuals with asthma, this small minority of individuals accounts for a large proportion of the asthma-related costs. Greater understanding of the pathophysiology of asthma combined with the emergence of novel biologic therapies for severe asthma supported the need for a thorough review of the diagnosis, investigation, phenotyping, and management of severe asthma. OBJECTIVES: We aimed to propose a practical approach to distinguish uncontrolled asthma due to inadequate asthma management from severe asthma despite optimal asthma management. Moreover, based on emerging scientific evidence, we sought to provide guidance for characterizing individuals with severe asthma and considering a phenotype-specific management. We also aimed to review other novel new potential therapeutic approaches. METHODS: We systematically reviewed the relevant literature focusing on randomized controlled trials and when available, systematic reviews of randomized controlled trials. The proposed key messages, based on scientific evidence and expert opinion, were agreed upon by unanimous consensus. MAIN RESULTS: We defined severe asthma and outlined its significant impact from the societal and patient perspectives. We outlined a practical approach to distinguish severe from uncontrolled but not severe asthma, based on stepwise investigation and management of potential reasons for uncontrolled asthma. After reviewing the current evidence we concluded that: 1) Several biomarkers (e.g. sputum or blood eosinophil count, total IgE, or FeNO) can help identify potential responders to new therapeutic options; 2) Tiotropium may be considered as an add-on therapy for individuals 12 years of age and over with severe asthma uncontrolled despite combination ICS/LABA therapy; 3) The chronic use of macrolides may decrease asthma exacerbations in individuals 18 years of age and over with severe asthma independent of their inflammatory profile; 4) Children aged 6 years and older and adults who are sensitized to at least one relevant perennial allergen and who remain poorly controlled asthmatics despite high dose ICS and a second controller can benefit from the addition of anti-IgE therapy to reduce asthma exacerbations; due to the known risk of side effects associated with high-dose ICS in children, omalizumab should also be considered in children and adolescents who repeatedly exacerbate or have poor control when therapy is stepped down from high-dose to moderate-dose ICS and at least one other controller; 5) Anti-IL5 therapies may be considered for adults 18 years of age and over with severe eosinophilic asthma who experience recurrent asthma exacerbations in spite of high doses of ICS in addition to at least one other controller; and 6) Although bronchial thermoplasty has shown a decrease in asthma exacerbations in one study, its role in the treatment of severe asthma remains uncertain.