US EPA

This report is intended to provide an overview of beta version 1.0 of the implementation of a model of repeated measures data referred to as the Toxicodiffusion model. The implementation described here represents the first steps towards integration of the Toxicodiffusion model into the EPA benchmark dose software (BMDS). This version runs from within BMDS 2.0 using an option screen for making model selection, as is done for other models in the BMDS 2.0 suite.

Time-course, or repeated (response) measures, data can be utilized to characterize toxic effects that are potentially evolving along critical time points. Neurotoxicity experiments, such as neurobehavioral screening studies, often produce time-course data. It may be advantageous for dose-response assessments to consider the time impact on the potential toxic effects. Thus, a model that provides predictions of responses as a function of both dose (exposure) and time should be available to provide relevant estimates (e.g., of BMDs) when a risk assessor must rely on such data. The software under consideration here is intended to be applied to such data to model the repeated measures (over time) of a single response metric, following various levels of exposure.

This report is intended to provide an overview of beta version 1.0 of the implementation of a model of repeated measures data referred to as the Toxicodiffusion model.

U.S. EPA. Benchmark Dose Software (BMDS) Development and Maintenance Toxicodiffusion Model (External Review Draft, Version 1.0). U.S. Environmental Protection Agency, Washington, D.C., 2008.