BRIEF COMMUNICATION Comparison of citrated native and kaolin-activated samples for thrombelastographic analysis in healthy dogs Sarah K. Flint 1 , R. Darren Wood 2 , Anthony C.G. Abrams-Ogg 1 , Stephen A. Kruth 1 , Alexa Bersenas 1 Departments of 1 Clinical Studies and 2 Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada Key Words Activator, canine, reference limit, TEG, tissue factor Correspondence Sarah Flint, Guardian Veterinary Centre, 5602 99th Street, Edmonton, Alberta T6E 1V2, Canada E-mail: sarah.flint@guardianvetcentre.com DOI:10.1111/j.1939-165X.2012.00431.x Background: Thrombelastographic (TEG) analysis is a test of global hemo- stasis in veterinary medicine; however, there have been limited compari- sons 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 simulta- neously 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 30 minutes (LY30) were recorded, and the concor- dance correlation coefficient (ρ 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 À1.3 minute, P = .0009), K (À0.7 minute, P = .0003), a (+5.1º, P = .002), MA (+2.4 mm, P = .002), and G (+568 dyn/cm 2 , P = .0009). LY30 was not different between methods. There was substantial agreement between methods for G (ρ c = .69) and MA (ρ c = .65), moderate agreement for R (ρ c = .45) and a (ρ c = .44), fair agreement for K (ρ c = .29), and slight agreement for LY30 (ρ c = .04). Conclusions: The TEG variables were significantly altered by kaolin activa- tion; 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. Thrombelastography (TEG) was first described in 1948 1 ; however, the relatively recent introduction of advanced software has increased its use in clinical prac- tice today. In human medicine, TEG has many applica- tions, including monitoring transfusion effects during cardiac and hepatic surgery, detecting hypocoagulable and hypercoagulable states, and monitoring anticoagu- lant and procoagulant therapy. 2,3 One of the main advantages of TEG is that it permits assessment of global hemostatic function within 30 minutes of specimen collection if fresh whole blood is used. However, citrat- ed whole blood is most often used in veterinary medi- cine due to the logistical difficulty of starting analysis within the recommended 5 minutes after collection. 4 Thrombelastography may be performed without activation or with an activator to shorten the reaction time, and use of human recombinant tissue factor (TF), kaolin, or no activator have been reported in the veterinary literature. 5–14 As TF initiates in vivo coagu- lation, it is the most physiologic activator; however, comparison among studies is challenging owing to use of different concentrations. 5–14 Human recombinant TF-activated TEG has been validated for canine citrated whole blood 13,14 and is being used increasingly for both research and clinical assays in veterinary med- icine. An alternative activator, kaolin, uses a buffered solution and phospholipids to induce coagulation by contact activation, and is suitable for analysis of Vet Clin Pathol 41/2 (2012) 249–255 ©2012 American Society for Veterinary Clinical Pathology 249 Veterinary Clinical Pathology ISSN 0275-6382