Relation of changes in PEF and FEV1 during bronchodilation in children.

INTRODUCTION: Asthma diagnosis can be confirmed through the observation of significant bronchodilator response (BDR) measured by peak expiratory flow (PEF) during home monitoring or by forced expiratory volume in one second (FEV1) with spirometry in a clinical setting. AIM: To use salbutamol administration after an exercise challenge test in children as a model of bronchodilation to assess how well relative change in PEF reflects improvement in lung function, as defined by increase in FEV1. METHODS: We retrospectively studied 326 free running exercise challenge tests with spirometry in children 6-16 years old. To assess congruency and differences between relative changes in PEF and FEV1 during bronchodilation, a regression analysis was performed, and a Bland - Altman plot was constructed. ROC analysis, sensitivity, specificity, positive and negative predictive values and Cohen's kappa coefficient were used to analyze how accurately increases in PEF predict an increase of 12% & 0.2 L in FEV1. RESULTS: Relative change in PEF was, on average, greater than that in FEV1. In ROC analysis, the area under the curve for PEF change was 0.837, with an optimal operating point of 14.5% (95% CI, 7.5-21.0%). The currently recommended cut-off for handheld PEF meters during home monitoring (15% increase) yielded a sensitivity of 71% and a specificity of 78%. The highest kappa value was observed at a 20% PEF cut-off. CONCLUSION: Increase in PEF is not an accurate measure of BDR compared with increase in FEV1. The patient populations identified using PEF and FEV1 criteria differ markedly.