Comparison of Δ FVC (% Decrease in FVC at the PC20) Between Cough-Variant Asthma and Classic Asthma

Abstract

The percentage decrease in forced vital capacity (FVC) at the methacholine PC20 (Δ FVC) has been proposed as a surrogate marker of maximal airway response. The aim of this study was to compare the Δ FVC between patients with cough-variant asthma (CVA) and those with classic asthma (CA). We performed a retrospective analysis of methacholine challenge test data from 47 children who were diagnosed as having CVA and from 75 children who had CA of mild severity. The mean (± SD) Δ FVC was significantly (p = 0.001) lower in the CVA group (14.7 ± 3.4%) compared with the CA group (17.1 ± 4.4%), whereas PC20 was not different between the two groups. Our results suggest that CVA is associated with a lower level of maximal airway response than CA.