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Comparisons of the distribution of subjects with varying degrees of airway responsiveness to methacholine and 4.5% hypertonic saline aerosols, and exercise challenges across different seasons. Mild/moderate/severe: methacholine PC20, 2-16/0.2-2/<0.2 mg/mL; 4.5% saline-PD15, 6-20/2-6/<2 mL; % fall in FEV1 after exercise, 15-25/25-50/>50%.
