Differentiation in dose-response curves of airway responsiveness to inhaled methacholine between asthmatics and...

We compared the discriminative capacity of the parameters obtained from dose-response curves of airway resistance (Raw) to inhaled methacholine (i.e., threshold dose, slope, and maximal increase in Raw) to differentiate asthmatics from nonasthmatics. Of the three parameters, maximal increase in Raw most accurately differentiated asthmatics from nonasthmatics (% correctness was 86% in asthmatics). Furthermore, an index consisting of both threshold dose and slope more clearly differentiated asthmatics from nonasthmatics (% correctness was 94% in asthmatics) than either threshold dose or slope alone (% correctness was 68% and 54% in asthmatics, respectively). We conclude, that of the three parameters, the maximal increase in Raw or an index consisting of both threshold dose and slope is the most discriminative index in asthmatics.