Poor reproducibility of template bleeding time in horses

Background: Template bleeding time (TBT) is considered to be a useful test for detecting platelet function disorders and the effect of platelet-activating drugs, but studies in human medicine have concluded that the test has poor reproducibility and sensitivity. Hypothesis: TBT has poor reproducibility in horses and has insufficient sensitivity to detect the effect of etamsylate on platelet function. Animals: Twenty healthy horses. Methods: TBT was determined and repeated 2 hours and 30 days later. TBT was also performed 2 hours after IV administration of etamsylate. Results: Although no statistical differences were seen between the TBT values obtained at different times, the coefficients of variation for TBT replicates ranged from 26.8% to 45.5%. The reference range for TBT was 138.4-860.4 seconds. No statistically significant shortening of the mean TBT value was observed after etamsylate administration. Conclusion and Clinical Importance: TBT has poor reproducibility, and the reference range is too wide to make TBT useful in a clinical setting. Other tests with higher reproducibility should be considered when assessing platelet function disorders in horses. Copyright © 2008 by the American College of Veterinary Internal Medicine.