A modular approach to validation: A work in progress

A modular concept to validate nonwhole animal test methods is proposed. The concept follows the definition, first suggested by Dr. John Frazier in OECD Environment Monograph 36, that validation is the use of a test for a specific purpose. The principles of the concept were all presented in a document describing a framework for validation by Goldberg et al. (1993). Within these principles, the concept prescribes validating a single in vitro assay independent of other in vitro assays. This modular concept evaluates the results obtained with a specific group or class of chemicals in an in vivo assay (validation standard). The same group of chemicals is evaluated for their response in an in vitro assay. The results in the in vivo and in vitro assays are compared to assess whether the in vitro assay predicts the in vivo response. A module consists of the chemical group, the validation standard, and an in vitro assay. A validation study may consist of several modules. In this case, one evaluates each module separately and therefore an in vitro assay is not compared to another in vitro assay.