Use of peak expiratory flow for assessing bronchodilator responsiveness.

Lung function in 1686 adult patients was measured before, and 15 minutes after, salbutamol inhalation. Bronchodilator responsiveness (BDR) was defined as a 12% improvement over baseline in either FEV1 or FVC, along with an absolute volume increment of 200 ml. Peak expiratory flow (PEF) change, both absolute and relative to baseline, was also calculated (DeltaPEF and DeltaPEF%, respectively). Change in PEF significantly correlated with change in FEV1. However, DeltaPEF and DeltaPEF% had poor discrimination in identifying BDR, with all specific cutoff values for DeltaPEF and DeltaPEF% having low or moderate sensitivity, specificity and predictive values.