A comparison of methods of benchmark-dose estimation for continuous response data

Methods of quantitative risk assessment for toxic responses that are measur ed on a continuous scale are not well established. Although risk-assessment procedures that attempt to utilize the quantitative information in such da ta have been proposed, there is no general agreement that these procedures are appreciably more efficient than common quantal dose-response procedures that operate on dichotomized continuous data. This paper points out an equ ivalence between the dose-response models of the nonquantal approach of Kod ell and West((1)) and a quantal probit procedure, and provides results from a Monte Carlo simulation study to compare coverage probabilities of statis tical lower confidence limits on dose corresponding to specified additional risk based on applying the two procedures to continuous data from a dose-r esponse experiment. The nonquantal approach is shown to be superior, in ter ms of both statistical validity and statistical efficiency.