Analysis of PC20-FEF25%-75% and △FVC in the methacholine bronchial provocation test

ABSTRACT

Purpose@#Forced expiratory flow between 25% and 75% (FEF 25%-75%) is known to sensitively reflect bronchial obstruction. Methacholine challenge test (MCT) has shown varying reduction levels of forced vital capacity (FVC) with the reduction in forced expiratory volume in 1 second (FEV1) in asthma. The aim of this study was to evaluate the clinical implication of provocative concentration causing a 20% fall in FEF 25%-75%(PC 20-FEF 25%-75%) and the percentage fall in FVC at the PC 20 dose of methacholine (△FVC). @*Methods@#A total of 194 children who visited the hospital due to respiratory symptoms and underwent MCT were analyzed retrospectively. The patients were divided into 3 groups. Group I had both PC 20-FEV1 and PC 20-FEF 25%-75% above 16 mg/mL; group II had a PC 20-FEF 25%-75% that fell below 16 mg/mL but PC 20-FEV1 was 16 mg/mL or above; group III had a PC 20-FEV1and a PC 20-FEF 25%-75% that both fell below 16 mg/mL. @*Results@#In group II, PC 20-FEV1 was lower (P = 0.026) and the rate of change in FEV1 and FEF 25%-75% from baseline to 16 mg/mL of methacholine concentration was greater than in group I (both P< 0.001). Levels of PC 20-FEF 25%-75% were higher in group II compared to group III (P < 0.001). △FVC showed a correlation with PC 20-FEV1 (P < 0.001) only in the whole group. @*Conclusion@#In asthmatic children, PC 20-FEF 25%-75% may be associated with bronchial hyperresponsiveness. △FVC was not associated with other parameters in either group. For subjects with a positive finding of PC 20-FEF 25%-75% and a negative finding of MCT, the progression to asthma can be suspected.