Comparison of components of biological variation between 3 equine thromboelastography assays.

This study analyzed the performance of thromboelastography (TEG), a test that measures blood clotting, in horses. The research compared three different types of TEG methods, looking at their sensitivity to sample handling errors and data variation, and tested how well normal ranges could be applied to results from these tests.

Context and Objective

• The researchers stated that there is a lack of detailed information about the performance of Thromboelastography (TEG), a method used to measure blood clotting, in horses.
• The aim of this study was to assess the impacts of pre-analytical variations (variations that occur before or during testing), to compare the observed variations in the analysis between three different TEG methods, and to determine how well population-based reference intervals (a commonly used range of ‘normal’ or healthy values) could be applied to these methods.

Methods

• A total of 20 healthy adult horses had blood collected once, and another 8 healthy adult horses had blood collected weekly for 5 weeks.
• Their blood was analyzed using three different TEG methods: one that did not use any activators (nonactivated TEG), and two that used either human recombinant tissue factor (TF) or kaolin to activate the blood clotting.

Results

• The results revealed considerable differences between the nonactivated test and the activated ones (TF TEG and kaolin TEG) for all parameters measured, with a higher degree of variation for the nonactivated test.
• The analytical variability – the degree to which the test results vary when the test is repeated – was reasonably low and similar across all three TEG methods.
• However, the nonactivated TEG was found to have the highest levels of within-subject variation, with the TF-activated test showing intermediate levels and the kaolin-activated test showing the lowest levels.

Conclusions

• The findings suggest that nonactivated TEG is more sensitive to preanalytical variation than both TF-TEG and K-TEG. The analytical variation was low for all assays, but not all parameters reached objective analytical goals.
• The results further suggest that population-based reference intervals can be readily used for TF-TEG, but not for nonactivated or K-TEG tests. The researchers propose that critical difference may provide a better interpretation criterion for these assays.