Carlson College of Veterinary Medicine

BACKGROUND: Clinical pathology of rodents is hindered by sample volume limitations. A single whole heparinized blood sample is often submitted for hematologic and clinical chemistry analysis in exploratory research settings, and sample dilution may be required. Published information on the potential impact of sample dilution and heparin use on hematology variables in rodents is sparse.

OBJECTIVES: The purpose of the study was to evaluate the effects of sample dilution and of anticoagulant on hematologic analysis of mouse and rat blood samples on the Sysmex XT-2000iV.

METHODS: Mice and rats were obtained from various ends of study research projects, and whole blood was collected via terminal cardiocentesis in lithium heparin, and additionally in EDTA when paired samples were obtained from rats. Hematology analytes were measured on the Sysmex XT-2000iV straight and diluted from ×2 to ×5.

RESULTS: Significant differences between heparinized samples analyzed straight vs diluted were found for MCV and MCHC, with a bias for several additional variables. Significant differences between paired heparinized and EDTA-anticoagulated samples at each dilution point were found for most variables, with the largest differences found in platelet count. Evidence of platelet clumping presumably due to heparin exposure was noted in numerous samples.

CONCLUSIONS: Dilution-induced changes occur in some hematologic variables and may render dilution unacceptable in the exploratory research environment. Many variables, most notably platelet count, differ based on the anticoagulant used, and values from heparinized vs EDTA-anticoagulated samples should not be directly compared.