Elevated eosinophils, IL5 and IL8 in induced sputum in asthma patients with accelerated FEV1 decline

Some patients with asthma present with accelerated lung function decline. This phenomenon is mostly associated with severe exacerbations and with poor asthma control.

Elevated sputum eosinophils, IL5 and IL8, which have a potential to stimulate airway remodelling, might be a useful non-invasive biomarkers and therapeutic targets of accelerated FEV1 decline in asthma patients.

We recruited 50 patients with mild asthma for pulmonary function testing and induced sputum sampling 12-15 years after the initial diagnosis. In 33 patients, from whom sputum of a good quality was obtained, inflammatory cells were counted and concentrations of cytokines IL-2, IL-4, IL-5, IL-8, IL-10, IFN-γ, angiogenin and VEGF in the sputum were measured by cytometric bead array.

Our aim was to detect the extent of FEV1 decline in patients with mild asthma and to discriminate clinical, functional and inflammatory factors associated with accelerated FEV1 decline.

Eighteen of 33 patients presented with accelerated FEV1 decline of more than 30 ml/year, with a mean (SEM) of 43.2 (3.9) ml/year, compared to 15 control patients with a FEV1 decline of 14.4 (2.1) ml/year. In the accelerated FEV1 decline group, we found elevated sputum levels of IL5 with a median (IQR) of 1.8 (0.4-3.2) pg/ml vs. 0.2 (0.1-1.2) pg/ml, p = 0.04; IL8 with a mean (SEM) of 1503 (194) pg/ml vs. 938 (177) pg/ml, p = 0.04; and eosinophils with a median (IQR) of 223 (41-1020) cells/μl vs. 39 (1-190) cells/μl, p = 0.03. No significant differences in other measured parameters were detected between the two groups.