Evaluation of the sensitivity and specificity of in vivo erythrocyte micronucleus and transgenic rodent gene mutation tests to detect rodent carcinogens

Sensitivity and/or specificity of the in vivo erythrocyte micronucleus (MN) and transgenic rodent mutation (TGR) tests to detect rodent carcinogens and non-carcinogens were investigated. The Carcinogenicity and Genotoxicity eXperience (CGX) dataset created by Kirkland et al. was used for the carcinogenicity and in vitro genotoxicity data, i.e., Ames and chromosome aberration (CA) tests. Broad literature surveys were conducted to gather in vivo MN or TGR test data to add to the CGX dataset. Genotoxicity data in vitro were also updated slightly. Data on 379 chemicals (293 carcinogens and 86 non-carcinogens) were available for the in vivo MN test; sensitivity, specificity or concordances were calculated as 41.0%, 60.5% or 45.4%, respectively. For the TGR test, data on 80 chemicals (76 carcinogens and 4 non-carcinogens) were available; sensitivity was calculated as 72.4%. Based on the recent guidance on genotoxicity testing strategies, performance (sensitivity/specificity) of the following combinations was calculated; Ames + in vivo MN (68.7%/45.3%), Ames + TGR (83.8%/not calculated (nc)), Ames + in vitro CA + in vivo MN (80.8%/21.3%), Ames + in vitro CA + TGR (89.1%/nc), Ames + in vivo MN + TGR (87.5%/nc), Ames + in vitro CA + in vivo MN + TGR (89.3%/nc). Relatively good balance in performance was shown by the Ames + in vivo MN in comparison with Ames + in vitro CA (74.3%/37.5%). Ames + TGR and Ames + in vivo MN + TGR gave even higher sensitivity, but the specificity could not be calculated (too few TGR data on non-carcinogens). This indicates that in vivo MN and TGR tests are both useful as in vivo tests to detect rodent carcinogens.