Article Text

Download PDFPDF

Slope of the dose-response curve: usefulness in assessing bronchial responses to inhaled histamine.
  1. D W Cockcroft,
  2. B A Berscheid


    The value of determining the slope of the histamine dose-response curve, in addition to the histamine provocation concentration producing a 20% reduction in FEV1 (PC20-FEV1), was assessed by analysis of histamine dose-response curves in 40 patients selected as having a wide range of increased non-specific bronchial responsiveness to inhaled histamine. The histamine dose-response curves were found to be fit the linear curve (dose v response, mean r2 = 0.97) better than the logarithmic curve (log dose v response, mean r2 = 0.93), the difference being significant (p less than 0.001). There was a strong negative correlation between the PC20-Fev1 and the slope (r = -0.98, p much less than 0.001) and a weak negative correlation between the PC20-FEV1 and the log-dose-response slope (r = -0.38, p greater than 0.05). Sixteen normal subjects and 16 asthmatic patients were compared on the basis of histamine dose-response curves measuring fal in sGaw. In this study there was no difference between r2 for the linear determination and for the logarithmic determination (0.91 v 0.90, p less than 0.05). The PC35-sGaw showed a strong negative correlation with the dose-response slope (r = -0.95, p much less than 0.01) and no correlation with the log-dose-response slope (r = 0.09, p greater than 0.05). In the two studies there appeared to be little information gained from the determination of either the dose-response slope or the log-dose-response slope. The slope and the PC20-FEV1 were equally reproducible, duplicate determinations showing less than a two-fold difference in 14 of 15 paired PC20 measurements and in 13 of 15 paired slope measurements. In summary, the slope of the histamine dose-response curve appears to fit the linear model better than the logarithmic model. It is feasible to calculate it from the results of a standardised histamine inhalation test; determination of either the slope or the log-dose-response slope, however, appears to add little useful information. It is recommended that bronchial provocation test results should be expressed in terms of a threshold concentration such as the PC20-FEV1 or the PC35-sGaw.

    Statistics from

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.