In common with most species, rodents as they age become progressively more
susceptible to naturally occurring diseases that can modify clinical pathology results and
thus obscure meaningful interpretation. Quantitative clinical chemistry and urinalysis
should, therefore, be generally avoided in rodents during their second year of life.
Clinical pathology evaluation in these animals, generally undertaken towards the end of a
carcinogenicity study, should be confined to a haematological evaluation of blood smears
taken from decedents and at study termination to aid in the interpretation and
differentiation of haemopoietic neoplasia. For both rodents and non-rodents, clinical
pathology testing should be performed on the same animals as examined for
morphological pathology findings and it is also recommended that blood samples from
recovery or withdrawal satellite groups should be analysed at study termination