Abstract
The National Toxicology Program (NTP) developed a standard approach for clinical pathology investigations that was integrated into most toxicity studies designed and conducted after 1986. Protocols for these studies include specific hematology and clinical chemistry analyses at 3 selected time points in 13-wk studies. Requirements concerning the anesthetization of animals, collection and analysis of samples, and reporting of results have been established to control sources of variability within and between contract laboratories that perform these studies for the NTP. Laboratories must meet minimum standards to be approved for participation in the Program. Important areas of consideration for these laboratories to perform clinical pathology investigations include the facility, equipment, personnel, performance, and quality control procedures. Clinical pathology results from approximately 60 13-wk studies that have been conducted by the NTP in 7 laboratories since 1987 are being analyzed to generate a database of control values for the Fischer rat and B6C3F, mouse and to identify sources of variability. Experimental data from these studies are being analyzed and correlated with histopathologic findings to evaluate the contribution of clinical pathology to the characterization of toxicity and to examine the appropriateness of the current approach. Efforts such as these will provide for the evolution and continued relevance of clinical pathology in toxicity testing.