Methacholine challenge testing: Safety of low starting FEV₁

Study objective: The lower limit for the baseline value to initiate methacholine bronchial hyperresponsiveness testing has not been well established. Recommendations have varied from > 1 L to above 80% of predicted. The objective was to determine if an FEV₁ <60% predicted was acceptable. Design: Retrospective analysis of challenges in 88 patients with a baseline FEV₁ of <60% predicted (mean=45.8%; range, 22 to 59%. Setting: Academic institutions. Results: There were only four individuals whose FEV₁ did not return to >90% of baseline following one poststudy β₂-agonist treatment. All four responded to a second treatment. There were no adverse sequelae following challenge in any individual. Neither age (up to 79 years) nor gender influenced outcome. Conclusions: In chronic moderate to severe asthma, it appears that bronchial hyperresponsiveness testing can be safely performed even in those patients with a low baseline FEV₁.