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 and thirty-two patients with severe late-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.