Statistical Procedures for Low Dose Extrapolation of Quantal Response Toxicity Data

Maximum likelihood procedures for fitting the probit, logit, Weibull and gamma multi-hit dose response models with independent, additive or mixed independent/additive background to quantal assay toxicity data are reviewed. In addition to parameter estimation, the use of the above models for low dose extrapolation is indicated with both point estimates and lower confidence limits on the “safe” dose discussed. A computer program implementing these procedures is described and two sets of toxicity data are analyzed to illustrate its use.