Peak expiratory flow as an endpoint for clinical trials in asthma: a comparison with FEV₁

The primary lung function endpoint in clinical trials in adolescent and adult patients with asthma is usually forced expiratory volume in one second (FEV₁). The objective of our analysis was to assess whether peak expiratory flow (PEF) is a suitable alternative primary lung function endpoint.

For this assessment, we calculated post hoc the correlation between pre-dose FEV₁ and pre-dose PEF measured under supervision in the clinic and, for both lung function parameters, the correlations between supervised clinic and unsupervised home measurements, using the results from the 8 Phase III parallel-group trials of the global clinical development programme with tiotropium Respimat® in patients with asthma aged 12 to 75 years.

Across all 8 trials included in this analysis, changes in lung function from baseline correlated well between pre-dose FEV₁ and pre-dose PEF when both were measured under supervision in the clinic. Correlation between supervised in-clinic and unsupervised home measurements was stronger for pre-dose PEF than for pre-dose FEV₁.

Pre-dose PEF measured at home could be an alternative primary lung function endpoint for trials in adolescent and adult patients with asthma. Using home-measured PEF could facilitate trial conduct and improve the convenience for patients by relocating scheduled assessments from the clinic to the patient's home.

Adolescents aged 12 to 17 years: RubaTinA-asthma® ( NCT01257230 ), PensieTinA-asthma® ( NCT01277523 ). Adults aged 18 to 75 years: GraziaTinA-asthma® ( NCT01316380 ), MezzoTinA-asthma® ( NCT01172808 / NCT01172821 ), CadenTinA-asthma® ( NCT01340209 ), PrimoTinA-asthma® ( NCT00772538 / NCT00776984 ). All from Clinicaltrials.gov ( https://clinicaltrials.gov/ ).