Validation and acceptance of new and revised tests: a flexible but transparent process

Scientific validation is a necessary prerequisite for the regulatory acceptance of new toxicological tests, and for acceptance as Organisation for Economic Co-operation and Development Test Guidelines. Validation is defined as the determination of the reliability and relevance of a test method for a particular purpose. Reliability refers to the reproducibility of the test within and among laboratories. The relevance of a test addresses how well it measures or predicts what it is supposed to measure or predict. There are no fixed values for how reliable or relevant a test should be. Acceptable values depend on the type of test, the inherent variability in the biological systems used, and what regulatory decisions the test will be asked to support. The validation of in vitro and in vivo tests should follow the same general principles. The validation process should be flexible, according to the type of test being evaluated and its proposed uses. If a test is designed to replace a test currently in use, its reliability and relevance should be measured against that reference test or against the effect that the test is designed to predict. For the evaluation of health effects where adequate human data are available, the performance of the new test should be measured against the relevant effect in humans, rather than a surrogate species. All proceedings from the validation process and the subsequent peer-review of the method should be transparent, i.e., publicly available. It is also recommended that the peer-review of the validation study be accessible to the interested public.