Chest
Clinical Investigations: AsthmaMethacholine Challenge: Comparison of Two Methods
Section snippets
Subjects
Subjects with asthma6 were recruited from the respiratory clinic at the Royal University Hospital and from advertisements. Inclusion criteria included an FEV1 ≥ 65% predicted and a tidal-breathing provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) < 16 mg/mL. The study was approved by the University of Saskatchewan Ethics Committee, and signed informed consent was obtained.
Study Design
Subjects (n = 40) attended the laboratory on 2 days at the same time of day within 1 week. Inhaled
Results
Forty subjects meeting the inclusion criteria of an FEV1 ≥ 65% and a tidal-breathing PC20 < 16 mg/mL completed the investigation without adverse events. A forty-first subject failed to return for the second methacholine challenge and was not included in the analysis. Demographics of the 40 subjects who completed both challenges are given in Table 1
Individual data points for the two methacholine challenges are compared in Figure 1. Three subjects with tidal-breathing PC20 values ranging from 1.9
Discussion
We have compared the two standardized methacholine challenges with the only differences in protocol being the method of aerosol generation and the method of inhalation. In the entire group, the geometric mean dosimeter PC20 was almost twice that of the tidal-breathing PC20. The discrepancy was greater (2.1-fold) in those with tidal-breathing PC20 > 1.0 mg/mL and less (1.6-fold) in those with tidal-breathing PC20 < 1 mg/mL. Adding to this discrepancy were an additional three subjects with
Acknowledgments
The authors thank Jacquie Bramley for assisting in the preparation of this article.
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Dr. Cockcroft is the Ferguson Professor of Respiratory Medicine
Supported by a grant from Methapharm Inc
Supported by the Lung Association of Saskatchewan