Veterinarska stanica, Vol. 51 No. 5, 2020.
Review article
https://doi.org/10.46419/vs.51.5.2
Coagulation assays in veterinary medicine
Andrea Tumpa
; Faculty of Veterinary Medicine, University of Zagreb, Croatia
Renata Barić Rafaj
; Faculty of Veterinary Medicine, University of Zagreb, Croatia
Abstract
Haemostasis is the process of stopping bleeding. Spontaneous haemostasis includes complex biochemical mechanisms of blood clotting, regulated interactions between injured tissue, blood vessels and circulating thrombocytes, procoagulants, anticoagulants, and fibrinolytic proteins. Haemostasis is divided into three phases: primary haemostasis, secondary haemostasis, and fibrinolysis. Nonfunctional primary haemostasis results in the slow and difficult formation of a platelet clot. In the event of an injury, blood will be
released from the blood vessels for a few seconds or minutes until a stable secondary haemostatic clot is formed. In the case of nonfunctional secondary haemostasis, bleeding is not observed immediately, but after a few minutes. Given the different stages of
haemostasis and various activation pathways, different laboratory measurement methods have been developed. This study outlines and describes the coagulation tests currently applied in veterinary practice. The method and the purpose of each test are described,
along with major remarks regarding sampling and possible interferences. Blood sampling for coagulation tests is more sensitive than sampling for other blood analyses. It is essential to avoid platelet activation and for this reason, ideal sampling would be
venepuncture without venous stasis. Most coagulation assays use platelet-poor plasma as a sample. The vast majority of haemostasis
measurements include monitoring clot formation (coagulum), i.e. monitoring the speed and ability or lack of ability to form a blood clot. Today, methods are automated and the time of the clot formation is measured by electro-mechanical or photo-optical methods. Additionally, it is possible to measure the activity of enzymes and coagulation inhibitors, and the concentration of individual components of coagulation cascades and fibrinolysis. In these cases, immunochemical methods based on the specific antigen-antibody
reaction are used. Thromboelastography is a relatively new method that is increasingly used. In contrast to standard coagulation tests, thromboelastography uses whole blood as a sample. This method evaluates the kinetics of the entire clotting process - from the initial formation of the clot, through polymerization of fibrin, to the final step of the formation of the stable secondary clot. Laboratory diagnostics begins with the global coagulation assays. Global coagulation assays
are the simplest and they cover both the intrinsic and extrinsic pathway. Assays that are included are bleeding time, prothrombin time, activated partial thrombolytic time, thrombin time, platelet count, and fibrinogen. To set a definitive diagnosis, it is necessary to
perform one or more specific coagulation tests. Specific tests include the analysis of activity and function of platelets, platelet antibodies,
and measurement of the concentration and activity of von Willebrand factor and clotting inhibitors (antithrombin and protein C). It is also possible to follow the course of fibrinolysis by measuring the concentration of fibrin and fibrinogen degradation products. Due to the complexity of the coagulation system, laboratory testing of haemostasis needs to be carried out in several stages, starting from several global assays and at least one specific. It is important to emphasize that there is no single test that can independently provide insight into the function of the entire coagulation system.
Keywords
haemostasis; coagulation; platelets; global coagulation assays; thrombocytopenia
Hrčak ID:
238185
URI
Publication date:
1.7.2020.
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