Randomized double-blind study (third place blinded) to examine the effectiveness and side effects of methacholine in the nonspecific bronchial provocation test

Softly and effectiveness of methacholine for the diagnosis of non-specific bronchial hyperresponsiveness [BHR] were tested in a third place blinded study. 61 patients suspected to suffer from BHR took part. 56 subjects provided complete data and were included in the study. 27 participants were challenged with methacholine 0.33% (verum) and 29 patients received NaCl 0.9% (placebo). The challenge was applied as 5-step-test using a storage bag. The doses were elevated by doubling the aerosol volume. A positive test result was assumed when basal specific airway resistance (sRt) reduplicated and simultaneously 2.0 (kPa*s) was attained. Ten out of 27 subjects in the verum group (33.3%) had a positive test result whereas in the placebo group only one subject showed a reaction (3.5%). A statistically significant association between the change of sRt and the cumulative methacholine dose was confirmed in the verum group (p < 0.002), whereas this effect could not be observed in patients challenged with placebo (p = 0.20). Side effects did not occur. We conclude that inhalative challenge with methacholine 0.33% applied as a 5-step-test is suitable to objectify BHR. The substantial benefit of the applied test scheme is the short range of time in which the challenge can be performed (approximately 20 min) and that dilution series of the test substance (methacholine 0.33%) are not required.