Comparison of citrated native and kaolin-activated samples for thrombelastographic analysis in healthy dogs

Background Thrombelastographic (TEG) analysis is a test of global hemostasis in veterinary medicine; however, there have been limited comparisons of analysis of citrated native and kaolin-activated samples. Objectives The purpose of this study was to determine the variation in TEG variables between citrated native and kaolin-activated whole blood samples and to establish reference intervals for both sample types. Methods Citrated whole blood samples were obtained from 40 healthy dogs. Thirty minutes after collection, TEG analysis was performed simultaneously on samples with and without kaolin-activation. Reaction time (R), clotting time (K), angle (a), maximum amplitude (MA), global clot strength (G), and clot lysis at 30minutes (LY30) were recorded, and the concordance correlation coefficient (?c) was calculated for each sample type. Results Significant differences between results obtained for kaolin-activated and native samples were obtained for R (mean difference -1.3minute, P=.0009), K (-0.7minute, P=.0003), a (+5.1 degrees, P=.002), MA (+2.4mm, P=.002), and G (+568dyn/cm2, P=.0009). LY30 was not different between methods. There was substantial agreement between methods for G (?c=.69) and MA (?c=.65), moderate agreement for R (?c=.45) and a (?c=.44), fair agreement for K (?c=.29), and slight agreement for LY30 (?c=.04). Conclusions The TEG variables were significantly altered by kaolin activation; however, some agreement between sample types suggests a consistent bias. In citrated whole blood activated with kaolin, clot formation time is shortened and the amplitude of the tracing is increased, resulting in a TEG tracing that appears to indicate relative hypercoagulability compared with that obtained using native citrated whole blood samples.