Assays, tests, assessment methods practices

It is tempting to classify all in vivo techniques as risk-assessment methods. For example, host-mediated-type studies have been incorrectly assumed to be more applicable to risk assessment than related in vitro studies. This is not necessarily true, since the genotoxic end points are still measured by in vitro test systems coupled with the animal host, and therefore the data are still valid only to detect potential. Attributing greater relevance to such tests may result in erroneous conclusions regarding safety or risk. Actually, there are very few practical risk-assessment assays available to evaluate genotoxicity, and our ability to extrapolate results from these to humans is uncertain, since evidence demonstrating mutation induction in humans is technically not possible. 

In practical terms, the assessment of relevance addresses the following question Given the information known about the alternative method, are the data provided by the assay good enough to allow its acceptance as a replacement for a given in vivo test In order to answer this question, all of the available information related to performance, operation, and mechanistic basis of an alternative method and the in vivo toxicity test it is intended to replace must be thoroughly reviewed. The benefits and risks associated with the adoption of the new method must also be defined. Once this information is available, it must be synthesized in a manner that allows those involved in a validation process to render a judgment that the performance of the alternative method is acceptable or not as a replacement for the in vivo toxicity test. 

Scope. The scope of assay validation is to assess the essential test method performance characteristics of accuracy, reproducibility, repeatability, linear-ity, and limit of quantitation/detection [41]. A test method is evaluated for its readiness for assay validation against the following criteria (1) description of the test basis and scientific purpose, (2) case for relevance, (3) proposed practical application,... 

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