Increase in blood eosinophil count over time and sputum IL8 are associated with FEV1 decline in asthma

<b>Background:</b> Asthma is associated with accelerated rate of FEV₁ decline. <b>Objective:</b> To determine predictive factors associated with accelerated FEV₁ decline in adult asthma and evaluate sputum cytokines as potential biomarkers for airflow decline. <b>Methods:</b> We recruited 125 asthmatics evaluated at the asthma clinic of Liège and reevaluated them at least 5 years later. Clinical, functional and inflammatory characteristics were compared between patients with accelerated decline (FEV₁ decline &gt;0.85% predicted.yr^-1) and others. Predictive factors were highlighted with linear regression analysis. Sputum EGF, VEGF, FGF, IL5, IL8, TGF-β, and IgE levels were measured in 58 of these patients at both visits by Human XL cytokine Luminex Performance assay and Elisa. <b>Results:</b> Post-BD FEV₁ decline was 0.06 ± 2.44% predicted. y^-1 in the overall population. Median (IQR) time between visits was 66 (62 – 86) months. The multivariable analysis showed that an increase in blood eosinophils over time (Δ BEC) (Reg. Coef. (95%CI): 0.002 (0.001 to 0.004), p=0.005)) and onset of asthma (0.04 (0.003 to 0.07), p=0.036) were independently associated with FEV₁ decline. IL8 levels measured at baseline were higher (499 (408 - 603) pg/ml, p=0.0040) in patients with accelerated decline compared to others (143 (88 - 308) pg/ml). <b>Conclusion:</b> In this study, we have confirmed that an increase in blood eosinophil counts over a follow-up of at least 5 years and later onset of asthma are associated with accelerated annual FEV₁ decline. Moreover, high sputum IL8 levels could be a risk factor for accelerated decline in asthma patients.