Estimation of minimum centrifugation time of microhematocrit tubes to obtain accurate results of packed cell volume and total solids in donkeys, dogs, sheep, and cows

To date, the minimum centrifugation times of microhematocrit tubes of blood to generate accurate PCV and total solids (TS) results have not been validated in veterinary medicine. We collected blood samples from 44 donkeys, 43 dogs, 61 sheep, and 40 cattle. We centrifuged microhematocrit tubes for 1, 2, 3, 5, and 15 min in donkeys and dogs, and 1.5, 3, 5, 10, and 15 min in ruminants. We evaluated the agreements between PCV and TS values at each time of centrifugation with the reference values at 15 min using intra-class coefficients of correlation and linear regressions. Finally, we considered the symmetrical distribution of differences between results obtained at each time of centrifugation and the reference values. We found that microhematocrit tubes centrifuged for a minimum of 3 min in donkeys and dogs, 10 min in sheep, and 5 min in cattle gave PCV and TS results in agreement with the values obtained after 15 min of centrifugation. The centrifugation time for cattle was shorter than currently advised. However, because PCV values of all cattle and most donkeys enrolled were within RIs and because no polycythemic animals were included, validation of these times may be warranted.