Forced Expiratory Flow (FEF25–75%) as a Clinical Endpoint in Children and Adolescents with Symptomatic Asthma Receiving Tiotropium: A Post Hoc Analysis

Introduction In pediatric patients with asthma, measurements of forced expiratory volume in 1 s (FEV1) may be normal or may not correlate with symptom severity. Forced expiratory flow at 25–75% of the vital capacity (FEF25–75%) is a potentially more sensitive parameter for assessing peripheral airway function. This post hoc analysis compared FEF25–75% with FEV1 as an endpoint to assess bronchodilator responsiveness in children with asthma. Methods Change from baseline in trough FEF25–75% and trough FEV1 following treatment with either tiotropium (5 µg or 2.5 µg) or placebo Respimat® was analyzed in four phase III trials in children (aged 6–11 years) and adolescents (aged 12–17 years) with symptomatic moderate (VivaTinA-asthma® and PensieTinA-asthma®) and mild (CanoTinA-asthma® and RubaTinA-asthma®) asthma. Data from all treatment arms were pooled and correlations between FEF25–75% and FEV1 were calculated and analyzed. Results A total of 1590 patients were included in the analysis. Tiotropium Respimat® consistently improved FEF25–75% and FEV1 versus placebo, although in adolescents with severe asthma, the observed improvements were not statistically significant. Improvements in FEF25–75% response with tiotropium versus placebo were largely more pronounced than improvements in FEV1. Statistical assessment of the correlation of FEV1 and FEF25–75% showed moderate-to-high correlations (Pearson’s correlation coefficients 0.73–0.80). Conclusions In pediatric patients, FEF25–75% may be a more sensitive measure to detect treatment response, certainly to tiotropium, than FEV1 and should be evaluated as an additional lung function measurement.