HISTORICAL HISTOPATHOLOGICAL CONTROL DATA FOR LABORATORY RODENTS - VALUABLE TREASURE OR WORTHLESS TRASH

The reasons for variation in longevity and disease incidence in untrea ted control animals in chronic toxicity and carcinogenicity tests in l aboratory rodents are reviewed and discussed. Genetic drift, dietary c omposition, caloric intake, age of animals at the termination of studi es, the skill, experience and diligence of the pathologist, the diagno stic criteria used and the appropriateness of statistical procedures a re considered to be the most important sources of variation. It is sug gested that more attention needs to be paid to the sources of nutrient s in animal diets and that 'closed formula' diets should be eschewed. The reliability of historical data depends critically on the extent to which 'like' can be compared with 'like'. The most important variable s in relation to histopathological data are considered in this context .