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Baseline characteristics of the subjects
Values are expressed as means±SD.
NS: not specific; Never smoker: no smoking history ever; Ex-smoker: no current smoking status for at least 3 months with previous smoking history; FVC: forced expiratory vital capacity; FEV1: forced expiratory volume in 1 second; pred%: percent of the normal predicted value; PC20: provocative concentration of methacholine causing a 20% fall in FEV1.
