The utility of methacholine airway responsiveness measurements in evaluating anti-asthma drugs.
Inman, Mark D. MD, PhD; Hamilton, Alan L. PhD; Kerstjens, Huib A. M. MD, PhD; Watson, Rick M. BSc; O'Byrne, Paul M. MB
[Miscellaneous Article]
Journal of Allergy & Clinical Immunology.
101(3):342-348, March 1998.
(Format: HTML)
Background: Measurements of airway responsiveness are frequently used to evaluate anti-asthma drugs.
Objective: This study investigated the utility of methacholine airway responsiveness measurements in evaluating anti-asthma medications, both in terms of a bronchoprotective effect and the ability to attenuate allergen-induced methacholine airway hyperresponsiveness.
Methods: Methacholine airway responsiveness was measured as PC20 on two occasions (separated by 35 /- 17 days, mean /- SD) in 40 subjects with mild, stable asthma. Additional subjects had PC20 measurements made before and after administration of either inhaled salbutamol (200 [mu]g) (n = 20) or allergen inhalation challenge (n = 31).
Results: The reproducibility of the methacholine PC20 with this method was high (intraclass correlation coefficient = 0.94). The average shift in PC20 after salbutamol was 4.11 doubling concentrations (SD = 1.08). On the basis of these results, a sample size of 12 subjects would be required to demonstrate a 1 doubling concentration difference in the bronchoprotective effect of two drugs with a 90% power. The average shift in PC20 after allergen was 1.29 doubling concentrations. On the basis of these results and an estimated SD of 0.96, a sample size of 24 subjects would be required to demonstrate that a drug is effective in attenuating 50% of allergen-induced airway hyperresponsiveness with a 90% power.
Conclusion: These results confirm the high reproducibility of methacholine PC20 measurements in subjects with mild, stable asthma and demonstrate its utility in evaluating the effects of anti-asthma drugs.
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