Relation of Changes in PEF and FEV₁ During Salbutamol-Induced Bronchodilation After Methacholine Challenge Test

Asthma diagnosis can be confirmed by observing significant bronchodilator response (BDR) through peak expiratory flow (PEF) at home or forced expiratory volume in 1 s (FEV₁) via spirometry in a clinical setting. We aimed to use the administration of salbutamol after a methacholine challenge test as a model of bronchodilation to study how accurately the change in PEF predicts improvement in lung function, as defined by an increase in FEV₁. We analyzed 869 adult patients who were administered salbutamol after a methacholine challenge. To compare relative changes in PEF and FEV₁ during bronchodilation, we used regression analysis and constructed a Bland and Altman plot. ROC analysis, sensitivity, specificity, positive and negative predictive values, and kappa coefficient assessed how precisely increases in PEF detected a 12% and 0.2-L improvement in FEV₁. The average relative increase in FEV₁ was significantly greater than that in PEF. The area under the curve in the ROC analysis was 0.844 for PEF change to detect a 12% and 0.2-L increase in FEV₁. The kappa values for changes in PEF and FEV₁ ranged from fair to moderate. BDR detected by the recommended 15% and 60 L/min cut-off for PEF identified less than half of true positives, while a 10% cut-off correctly identified close to 75% of them. PEF increase is not a reliable measure of BDR in comparison to FEV₁ increase, and a 10% improvement in PEF was the least inaccurate cut-off. Substituting the PEF meter with a handheld spirometer should be further investigated for asthma home monitoring.