Doses and models in risk assessment analysis for bronchial hyperresponsiveness

The aims of this study are: (1) to evaluate whether the estimates of the association of risk factors with bronchial hyperresponsiveness (BHR) depends on the accumulated dose administered in challenge tests; and (2) to verify whether a model developed for survival studies (Weibull regression) is suited to analyze methacholine dose-response curves. For these purposes, 863 challenge tests, from EC Respiratory Health Survey in Italy, up to a cumulative dose of 6 mg methacholine, were analyzed by Weibull regression and by traditional methods (logistic model and linear model), both before and after truncation of the curves at 2 mg. With all methods the main risk factors for BHR were respiratory symptoms and atopy while age and airway caliber exerted a protective action. Our results confirmed that in epidemiological surveys 2 mg methacholine is enough to fully appreciate the effect of risk factors on BHR and showed chat the Weibull model explains the observed variability better than linear and logistic regressions. (C) 1998 Elsevier Science Inc.