Within-laboratory reproducibility of Ames test results: Are repeat tests necessary?

A cross-sector group of experts from the Health and Environmental Sciences Institutes (HESI)'s Botanical Safety Consortium (BSC) and Genetic Toxicology Technical Committee (GTTC) analyzed data from the National Toxicology Program (NTP) Ames test database to evaluate the need for repeat testing when assessing the mutagenic and carcinogenic potential of chemical compounds.

Key Findings:

• High reproducibility for initial positive and negative responses from the National Toxicology Program (NTP) Ames test database for 3000 test articles.
• Repeating tests for initial positive and negative responses may be unnecessary in most cases.
• Lower reproducibility for initial equivocal responses suggests a need for repeat testing.
• Factors affecting reproducibility could include potency of the initial response, solubility of test substances, and laboratory experience.

Implications:

• Supports the OECD Test Guideline of not needing to repeat clear negatives and positives.
• Findings could inform revisions in testing guidelines.
• Findings could apply to single chemicals or mixtures such as botanical.

These results can provide context for determining the optimal design of recommended test protocols for use in screening both individual chemicals and complex mixtures, including botanicals.

Read the full paper: Within-laboratory reproducibility of Ames test results: Are repeat tests necessary? Zeiger et al., April 2024. Environmental and Molecular Mutagenesis. https://doi.org/10.1002/em.22597