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Amesfit: A microcomputer program for fitting linear‐exponential dose‐response models in the ames salmonella assay
Author(s) -
Leroux Brian G.,
Krewski Daniel
Publication year - 1993
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/em.2850220205
Subject(s) - ames test , salmonella , linear model , exponential function , statistics , poisson distribution , biological system , computer science , toxicology , mathematics , biology , genetics , bacteria , mathematical analysis
The Ames Salmonella/microsome assay remains the most widely used microbial test for genotoxicity. In this article, we describe a microcomputer program developed to fit a linear‐exponential dose‐response model to Ames assay data for established mutagens. The model includes a linear term to describe the mutagenic effects of the test agent at low to moderate doses and an exponential attenuation factor to accommodate downturns at high doses due to cytotoxicity. Quasi‐likelihood methods are used to obtain estimates of the unknown model parameters, thereby avoiding the need to fully specify the distribution of the experimental data. This method of estimation also allows for extra‐Poisson variation that is characteristic of counts of mutant colonies of bacteria observed in the Ames assay. The particular linear‐exponential model used here was developed for use in the analysis of a recent large‐scale collaborative trial using the Ames assay sponsored by the International Programme on Chemical Safety. The use of our program is illustrated using sample data sets taken from that collaborative study. © 1993 Wiley‐Liss, Inc.