Ensuring quality of in vitro alternative test methods: issues and answers.

Many in vitro and ex vivo methods have been developed or are under development to reduce or replace animal usage in toxicity tests. Consistent with the goal of obtaining scientifically sound test data for hazard and risk assessment of chemicals, changes are being made in current policies and procedures to facilitate the acceptance of data developed using these methods. National and international organizations are developing policies and standards for scientific practice to assure quality in implementation of in vitro methods. Consensus is developing in the scientific community for the quality control measures needed for in vitro methods; including appropriate controls, data reporting elements, and benchmarks to be identified in test guidelines so that the potential risks of chemicals can be reviewed and reliably assessed. Additional guidance to the OECD's Good Laboratory Practice principles [Organization for Economic Cooperation and Development (. Advisory Document of the Working Group on Good Laboratory Practice: The Application of the Principles of GLP to in vitro Studies. OECD Series on Principles of Good Laboratory Practice and Compliance Monitoring Number 14 (ENV/JM/MONO(2004)26). Paris, France] will help to ensure that in vitro tests used for regulatory purposes are reproducible, credible, and acceptable. Generic test guidelines incorporating performance standards are being written to allow acceptance of proprietary test methods by regulatory agencies and to provide assurance that any in vitro system performs over time in a manner that is consistent with the test system as it was originally validated.