Strategy for genotoxicity testing: hazard identification and risk assessment in relation to in vitro testing

Area of Science:

• Toxicology
• Genetic Toxicology
• Risk Assessment

Background:

• Regulatory agencies require genetic toxicology testing batteries.
• High rates of positive in vitro findings occur for non-carcinogenic agents.
• Need for standardized interpretation and follow-up testing strategies is recognized.

Purpose of the Study:

• Develop recommendations for interpreting in vitro genetic toxicology test results.
• Propose a strategy for follow-up testing after positive in vitro findings.
• Establish consensus principles for hazard identification and risk assessment.

Main Methods:

• Convened an Expert Working Group with international authorities from industry, government, and academia.
• Utilized a consensus process to develop guiding principles and a decision tree framework.
• Analyzed case studies based on actual test results to inform consensus opinions.

Main Results:

• A framework and decision tree were developed for assessing the need for and selection of follow-up tests.
• Criteria were defined for determining when positive in vitro results indicate low or no concern.
• Factors for follow-up testing include reproducibility, cytotoxicity, and historical control data.

Conclusions:

• Consensus principles for interpreting and following up on in vitro genotoxicity tests were established.
• The strategy aims to improve the relevance of genetic toxicology testing to human health risk assessment.
• Further refinement of specific test recommendations beyond initial batteries was not completed due to time constraints.