This study was a multicenter, open, observational study. The study was divided into two stages; the first stage of the study included a population with suspected asthma and performed a bronchial provocation test, and cumulative provocation dose when forced expiratory volume in one second (FEV1) fell by 20% (PD20 ) data were recorded. Subjects with positive excitation were treated as asthma for 3 months and treatment was considered effective to confirm the diagnosis of asthma. Sensitivity, specificity, and reliability of the methacholine choline provocation test were calculated, and cutoff values were obtained by exploratory analysis based on PD20 values. All patients clinically evaluated for bronchial provocation testing were included in the stage II study to further validate the diagnostic value and cutoff value of the methacholine choline provocation test.
