Validation via Weight-of-Evidence Approaches

Early discussions on evaluating the reliability and relevance of non-animal tests for particular purposes, i.e. on their validation, focused on the performance of practical multi-laboratory studies (Balls et al., 1990, 1995). However, it subsequently became clear that such practical studies would not always be necessary or even possible, and that, in some circumstances, a weight-ofevidence approach would be more appropriate, i.e. an evaluation based on the independent collection and assessment of appropriate and sound pre-existing supporting evidence. For example, there could be evidence of sufficient volume and quality to permit an evaluation of a method which had long been in use. In other cases, there might not be in vivo benchmark data of sufficient breadth and quality to serve as acceptable reference standards for the practical evaluation of an in vitro method.