Analysis of agreement among findings of pathologists in ED01 experiment.

The ED01 experiment, which involved determination of the effective dose to produce a 1% tumor rate, was carried out by the National Center for Toxicological Research (NCTR). The study involved greater than 20,000 BALB/c female mice exposed to various doses of 2-acetylaminofluorene, a chemical known to produce bladder and liver carcinomas. After death, tissues from each animal were evaluated for the presence of several types of tumors by one of a team of NCTR pathologists. After the ED01 experiment was completed, the Society of Toxicology commissioned another pathologist to carry out an independent review of the bladder and liver specimens from a stratified sample of the mice. There were substantial differences in the diagnoses of both tumor types by the pathologists, but the implications for detection of a dose-response relationship are important only for liver carcinomas.