Objective: Asthma is a common heterogeneous disease characterized by airway inflammation and bronchoconstriction. Current treatment guidelines provide recommendations for categorizing disease severity, asthma control and management. This paper reviews asthma assessment in primary care and describes the pathophysiology, clinical characteristics and new targeted treatments available for patients with severe eosinophilic asthma. Methods: A non-systematic PubMed literature search was conducted and articles, primarily from the last 5 years, were selected based on relevance to primary care practice, asthma pathophysiology and biologic therapies. Results: Despite optimal therapy including high-dose inhaled corticosteroids (ICS), long-acting β2-agonists and tiotropium, ∼4-10% of all patients with severe asthma continue to have poor asthma control. These patients have impaired quality of life, frequent exacerbations and are exposed to the side effects of repeated courses of oral steroids. Approximately 50% of patients with severe uncontrolled asthma have eosinophilic asthma, with increased airway expression of type 2 cytokines IL-4, IL-5 and IL-13. Eosinophilic asthma is identified in primary care by having eosinophils ≥150-300 cells/μL on a complete blood count with differential. Conclusions: A new class of agents is available for patients with moderate to severe eosinophilic asthma. Four biologic therapies - mepolizumab, reslizumab, benralizumab and dupilumab - that interfere with the regulation and activity of eosinophils have been approved by the FDA for patients with moderate to severe asthma with an eosinophilic phenotype. Primary care physicians should be familiar with these medications to explain part of the rationale for referral to specialist care and manage patient expectations for treatment.
Keywords: Eosinophils; IL-5; asthma; biologics; primary health care.