Background: The purpose of this study was to develop a rapid and safe methacholine provocation protocol equivalent to the standard dosimeter technique.
Methods: The rapid protocol comprised a short and a long subprotocol. The challenge was started with one of these subprotocols according to the subject's answers to a questionnaire and baseline lung function. If FEV1 dropped by 10% during the short subprotocol, the test was continued with the long subprotocol. The concentrations of methacholine and numbers of inhalations were chosen to match the concentrations of the standard method as closely as possible. To verify the protocol, we compared both methods in 38 subjects with asthma and 10 control subjects.
Results: The provocative concentrations of methacholine (PC20FEV1) obtained with the standard method and the rapid method were within one doubling concentration in 38 of 40 subjects. None of the subjects who were normoreactive according to the standard method (PC20FEV1 > 8 mg/mL) responded in the rapid protocol. The standard method required, on average (+/-SD), 34+/-11 min; the rapid method required 15+/-3 min.
Conclusions: The rapid provocation protocol is equivalent to the standard method, without loss in precision and safety, but with considerable saving in time. Therefore, it appears to be particularly suited for studies that require comparability with provocative concentrations obtained with the Rosenthal-Chai dosimeter method.