Follow-Up to In Vivo Testing

In case of positive results The compound is an in vivo somatic cell mutagen and testing for germ cell mutagenicity may be required. 

In case of negative results Further in vivo testing is required only in the case of positive in vitro studies again, the second in vivo test is chosen on a case-by-case basis as stated above. If the test is negative, it is concluded that there is no evidence for in vivo mutagenicity. 

In case of equivocal results Equivocal results may be due to low statistical power, which can be improved by increasing the number of treated animals and/or scored cells. If the situation is unresolved, a second in vivo test is required, chosen on a case-by-case basis (ordinarily on a different endpoint or in a different tissue, depending on toxicokinetics, metabolism, and mode of action) proceed according to Positive or Negative.  

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