Analysis of the methacholine dose-response curve: usefulness of a simplified log-logistic model in epidemiological studies.

The object of the study was to find a model to summarize all the information from dose-response curves, by determining the coefficients to be used to compare groups of subjects. Three coefficients were calculated from the following model: F(d)/F(o) = ONE - k(d-delta)alpha+, where F(d)/F(o) was the ratio between FEV1 at dose (d) of methacholine and prechallenge FEV1, 'k' the slope of the relative variation of FEV1 with the dose, 'delta' the threshold dose and 'alpha' a shape factor. The model was applied to the study of hyperresponsiveness in a population of 317 men. The results illustrated the interest of this model which was applicable to 91% of the population and permitted fine discrimination of the groups studied.