The Salmonella/microsome mutagenicity index revisited
statistical performance evaluation and modified measures
Palabras clave:
Ames test, Bias, Bootstrap, Confidence intervals, OverdispersionResumen
The Ames test is a widely used, short-term mutagenicity assay for environmental and human health risk assessment and its results are usually expressed by means of a simplistic measure, namely the mutagenicity index (MI). In this study, we aimed at evaluating its statistical properties, its advantages and disadvantages (point and interval estimation performances) in comparison to three new, similar measures (MIm, \tilde{MI} and \tilde{MI}_{m}). We used computer simulations of realistic, protocol-recommended scenarios, and illustrated our methods with an observed, real dataset. Our major findings are the following: (i) all four measures are generally unbiased; (ii) both bias and variance raises with overdispersion; and (iii) only the MIm is guaranteed to meet the nominal confidence level in interval estimation. Along with other recommendations, we present a discussion on the implications of the misuse of any these indices.
Citas
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