CANINE BONE-MARROW CYTOLOGY AS A MEANS OF SUPPORTING PERIPHERAL-BLOODCHANGES - THROMBOCYTOPENIA DURING THE COURSE OF A TOXICITY STUDY

The origin of induced changes in the peripheral blood frequently resid es in the bone marrow. Although interim (within study) canine bone mar row analysis provides crucial and vital information supplementary to s uch changes, it is not a routine technique in normal toxicity studies. A two-tiered approach is reasonable and scientifically justified, wit h haemocytometry as the first tier, and interim bone marrow analysis a s the second, only to be performed if indicated by peripheral blood va lues. Additionally, ethical and economic reasons play a decisive role in not performing interim canine marrow sampling on a routine basis, b ut only on selected occasions. Such an occasion would be the presence of a thrombocytopenia, where an objective assessment of megakaryoblast /megakaryocyte numbers and morphology would be a distinct advantage in determining the aetiology of the condition. However, such evaluations are normally hampered by the relatively small numbers of these cells, and a method for overcoming this problem is described.