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Benchmark Dose Software (BMDS)

Summary of Recent External Reviews of BMDS Models

2008 External Review of the Concentration x Time (ten Berge) Model

In June, 2008, a new Concentration x Time (ten Berge) model was externally reviewed by experts in modeling and statistics. The intentions of EPA with respect to this model were to (1) replicate CNxT model that Wil ten Berge originally implemented in Visual Basic in the C program language for use in BMDS and (2) develop comprehensive documentation for the model's use in BMDS. Thus, the primary charge to the external reviewers was to determine whether these intentions were adequately met. While providing comments on how the software might be improved, the reviewers' comments (PDF) (26 pp, 524K,  About PDF) indicated that the first intention was generally met and offered a number of improvements to the model documentation. The current, downloadable version of the model and its documentation take into account these comments.

2007 External Review of the Multistage Weibull Time-to-Tumor Model

In June, 2007, a new time-to-tumor multistage Weibull model ("MSW") was externally reviewed by experts, with reviews generally positive and confirmed that the functioning of the computer code had been rigorously tested. The reviewers' comments are provided with EPA's responses (finalized in 2008, after revisions to the program and documentation followed by more testing). [For more information]

2007 External Review of New Quantal Models

New quantal dose-response models having alternative background parameters were externally reviewed by experts in June, 2007. These models are available for testing in the beta test version of the new BMDS 2.0 beta. Reviews were generally positive and confimed that the functioning of the computer code has been rigorously tested. The reviewers' comments and EPA's responses are provided with the model development and testing report.

The new models are modifications of the current quantal models in BMDS. They were developed by modifying existing source codes, changing the code only as necessary. Addition of these new models to the suite of models in BMDS expands the range of alternatives available for fitting dose-response curves using generally accepted types of models.

Five new models implement an alternative form of background term, one that is additive to the dose. These are the multistage, cancer, log-probit, gamma, and Weibull models. The current versions of these models have a background term that is directly additive to the response probability. Models with background terms additive to dose were proposed and analysed in peer-reviewed papers by leading experts over 20 years ago, so they are not new to risk analysis. One type of model, log-logistic, will not be provided in a version with background additive to dose, because of technical difficulties causing unreliable convergence on solutions.

Two quantal models, probit and logistic, that currently have no explicit background response parameter will become available in that form.

Thus, with the exception of the log-logistic, all the BMDS quantal models will be available in BMDS 2.0 beta in two versions, differing in the background term. Current versions of quantal models keep the names used in BMDS 1.4.1c. New versions with an alternative background parameter are distinctively named to identify them clearly, e.g., "Weibull-BgDose", or "Probit-BgResp". [For more information]

2007 External Review of the Exponential Model
In September, 2007, a new Exponential model was externally reviewed by experts (PDF) (16 pp, 381K,  About PDF), with reviews generally positive and confirmed that the functioning of the computer code had been rigorously tested.  The current, downloadable version of BMDS incorporates a finalized version of the Exponential models, taking into account these comments.

2000 External Review of BMDS Version 1.1b and EPA Responses
Numerous comments were received by 24 reviewers (PDF) (1 pg, 113K,  About PDF) of the original BMDS beta test version (version 1.1b). Reviewers were impressed with its capabilities, potential and overall user friendliness. Reviewer comments (PDF) (8 pp, 394K,  About PDF) covered all aspects of the software, including the interface, model reliability, model output, harware compatibility and documentation.

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