Bone marrow (BM) cytology and histopathology are complementary tools used to investigate haematological diseases. Site of acquisition is normally based on clinician preference. The purpose of this study was to investigate if there are significant site-dependent differences in the diagnostic quality of samples from different locations. In this study diagnostic concordance, between histology and cytology, and at different acquisition sites was tested in 18 dogs euthanaised for reasons other than haematological diseases. Sequence of acquisition of the samples was randomised. BM was collected for cytology and histology from both humeri and ileal crests immediately after euthanasia. Cytology and histology was interpreted independently by a board-certified pathologist and clinical pathologist respectively. Data was analyzed using a linear mixed model that included fixed effects for site, method and the interaction between site and method, with a random effect for dogs. The myeloid: erythroid ratio (MER) was log transformed for symmetry. Site of BM acquisition did not affect sample quality or diagnosis by cytology or histology. In general, the MER from the ileal crest was larger than the MER from the humeri, and there were significant differences in the MER between histology and cytology. Pairwise comparisons found significant differences in cytological MER between the left humerus and left ileal crest and left ileum and right humerus. In conclusion, differences in MER between different BM sites in apparently healthy dogs did not affect the overall interpretation of the BM, but this may not apply to sick dogs.

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