Increase in blood eosinophils during follow-up is associated with lung function decline in adult asthma.

Background: Asthma is associated with accelerated rate of lung function (FEV ₁ ) decline.
Objective: To determine predictive factors associated with FEV ₁ decline in adult asthma.
Methods: A retrospective study was conducted in 229 asthmatics recruited from the University Asthma Clinic of Liege. Subjects had at least two visits with post-bronchodilation (post-BD) FEV ₁ and minimum one year between them. A multivariable linear regression analysis was conducted in order to come up with factors associated with lung function decline.
Results: Post-BD FEV ₁ decline in % predicted. y ^-1 was 0.2 (95%CI -2.0 to 2.8) in the overall population. Our population was made up of mild to moderate asthmatics [1] for 58%, aged 50 (41-60) years old, 62% were female and 59% were atopic. Median ICS dose was 1000 μg beclomethasone equivalent (CFC)/day with 81% treated at baseline. Time between visits was 46.8 ± 32.1 months. The univariate linear regression analysis revealed a negative association between % predicted FEV ₁ decline and baseline ACQ (p < 0.0001) and blood eosinophils (% and/mm ³ ) (p < 0.0001 and p < 0.0001). A positive association was found between % predicted FEV ₁ decline and baseline pre-BD FEV1 (mL) values (p = 0.001), blood neutrophils (%) (p = 0.02), change in blood eosinophils (%) (p < 0.0001), time between visits (months) (p < 0.0001). The predictive variables for accelerated decline highlighted by the multivariable analysis (r ²  = 0.39) were change in blood eosinophils (%) over time (p = 0.002) and time between visits (months) (p < 0.0001).
Conclusion: These findings highlight a new value for blood eosinophil counts as their increase over time predicts greater lung function decline in asthma.
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