BHR | Histamine PD15 ≤1.6 mg |
Marked BHR | Histamine PD15 ≤0.4 mg |
BHR severity [13] | |
Severe | PD15 ≤0.100 mg |
Moderate | PD15 0.101– ≤0.400 mg |
Mild | PD15 0.401– ≤1.600 mg |
None | PD15 ≥1.601 mg |
Normal FEV1 | ≥80% pred |
Normal FVC | ≥80% pred |
Normal FEV1/FVC | ≥88% pred |
Normal MEF50 | ≥63% pred |
Physician-diagnosed asthma | Subjects who answered “yes” to the question: “Have you been diagnosed as having asthma by a physician?” |
Childhood wheeze | Subjects who answered “yes” to the question: “Have you been diagnosed as having asthma or have you had wheeze in childhood?” |
Atopy | At least one positive skin prick test reaction to any of the tested allergens or reported symptoms of allergic rhinoconjunctivitis |
Nonsmoker | Never-smoker or smoking <4 cigarettes per month |
Ex-smoker | Those who had quit smoking ≥12 months prior to the study |
Exposure to ETS | The subjects were asked three separate questions about ETS: “Have you ever been exposed to environmental tobacco smoke at home/at work/generally in the surroundings?” The answer alternatives of all three questions were: “never”, “yes previously, not any more” and “yes, currently” |
ETS exposure ever | ETS at home or at work, or both, currently or previously |
ETS exposure present | ETS currently at the time of the study at home, at work, or both |
BHR: bronchial hyperresponsiveness; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; MEF50: maximal expiratory flow at 50% of FVC [21]; ETS: environmental tobacco smoke; PD15: provocative dose of histamine inducing a 15% fall in FEV1; % pred: % predicted.