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.