Biostatistical assessment of mutagenicity studies by including the positive control.

Statistical analysis plays a fundamental part in the evaluation of mutagenicity experiments. However, a statistically significant or non-significant test result without incorporating the biological relevance cannot be a valid scientific criterion for concluding a positive or negative effect of the underlying compound (Hauschke et al., 1997). The classification of an experiment as being negative or positive should be based also on the magnitude of the responses in the positive control. We address the problem of determining the maximum safe dose by incorporating a biologically meaningful threshold value, which is expressed as a fraction of the difference between positive and vehicle control.