Severe asthma is a distinct type of asthma that affects
Approximately 50% of patients with severe asthma have persistent airway tissue eosinophils—despite continued high-dose systemic and inhaled steroids.11
Elevated eosinophil levels are associated with chronic airway inflammation and obstruction in severe asthma, resulting in increased symptoms and exacerbations in your patients.1,11
The chronic inflammation caused by eosinophils may result in harmful structural changes to the airway walls, known as remodeling. This inflammation could also cause damage resulting in airway smooth muscle contraction, loss of lung function, and airway hyperresponsiveness.12 Remodeling can both increase the frequency and worsen the severity of exacerbations.1
Multiple cell types, including eosinophils, are involved in airway inflammation.13 Regulating eosinophil levels and inflammation could therefore be critical to managing severe asthma.12
However, given the evolving science around the role of eosinophils, the amount needed to balance their harmful inflammatory qualities and their protective immunoregulatory role is unknown.8,12
For patients with severe asthma, elevated blood eosinophil counts have a strong correlation with increased exacerbations.13 In fact, patients with eosinophil levels ≥300 cells/μl were shown to have exacerbations at rates nearly four times higher than patients with persistent asthma.18 But what levels should you consider when initiating treatment?
Although there is not yet an exact consensus for initiating treatment of patients with severe eosinophilic asthma, different baseline blood eosinophil levels have been evaluated for different biologic therapies (eg, ≥150 cells/μL, ≥300 cells/μL, and ≥400 cells/μL) that may help identify patients who could benefit from treatment.19,20
References
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