Increased levels of serum IL-17 and induced sputum neutrophil percentage are associated with severe early-onset asthma in adults

Background Differences between adult patients with severe early-onset and late-onset asthma have not been well studied. Objectives To determine the phenotypic distinction regarding age at onset in patients with severe asthma. Methods The present study enrolled thirty-two patients with severe early-onset (onset age 12 years) asthma. Severe asthma was defined according to Global Initiative for Asthma criteria. The clinical, spirometric, and laboratory parameters were collected for group comparisons. Results Among the 64 patients included (mean age, 46.22 ± 13.90 years; 53.1% male), the mean percent of predicted forced expiratory volume in 1 s (FEV1) was 68.43 ± 20.55%. Patients with severe early-onset asthma had a younger age, longer duration of asthma, higher rate of family history, and better small-airway function (MEF25% and MMEF75/25%) compared with severe late-onset asthma. Furthermore, levels of serum IL-17 and sputum neutrophil percentage were significantly higher for patients with severe early-onset asthma (P = 0.016, 0.033, respectively). Multiple logistic regression analysis revealed that increased serum IL-17 (odds ratio = 1.065, P = 0.016) was independently associated with severe early-onset asthma. The combination of serum IL-17 and sputum neutrophil percentage yielded a sensitivity of 80.0% and a specificity of 86.7% for identifying patients with severe early-onset asthma. Conclusions Patients with severe early-onset asthma exhibit elevated levels of serum IL-17 and sputum neutrophil percentage, suggesting a potential role in the pathogenesis of severe early-onset phenotype.