Evaluation of organ weight differences in toxicological experiments.

The most frequent measure used to interpret drug effects on organ weights in toxicological experiments is the ratio of the organ weight to the animal's bodyweight. It is shown that in general this measure is not useful and can lead to erroneous conclusions regarding drug effects, specifically for rats. In addition a new approach to the design of organ weight experiments is considered and compared to the use of relative weights using simulated data. It is concluded that this new method may be useful in the evaluation of organ weights.