Study of the small airway and its role in pediatric asthma control assessment

Background: Previous reports suggest that small airway dysfunction (SAD) is associated with asthma control. Objective: To determine the usefulness of the study of the SAD in assessing asthma control in children. Methods: A cross-sectional study was performed in children aged between 6-15 years old diagnosed with persistent asthma (GINA 2014) and FEV 1 >80% at the time of inclusion. A forced spirometry, a bronchodilator test, a determination of R5-R20 by IOS and a plethysmography were performed. Exhaled NO at multiple flow rates (30, 150, 250 ml/s) was measured and CA NO was calculated. Asthma Control Questionnaire Test (ACT) was completed. The prevalence of the SAD was defined by the presence of one or more of the following criteria: CA NO ≥4.5ppb, RV/TLC ≥33% and R5-R20 ≥0.147kPa/L/s. The association among CA NO , R5-R20, RV/TLC and ACT was studied using Spearman9s rho. The degree of agreement regarding asthma control assessment was studied using Cohen9s kappa (Kc). Results: 50 subjects were studied distributed into group 1 (poor control, n=16) and 2 (good control, n=34). At least 1 criteria of SAD was found in 29 (58%) and 2 criteria were found in 14 (28%). R5-R20 was increased in 24 (48%), RV/TLC in 8 (16%) and CA NO in 5 (10%). CA NO was significantly higher in group 1 (ppb) 1.65 (0.2-9.4) vs 1.45 (0.1-15). No agreement was found to establish the degree of asthma control among the rest of the variables studied. Conclusion: SAD was found in more than half of persistent asthmatic children. In our sample, only CA NO provides additional information to assess asthma control.