Study on biological variation of haemostatic parameters in clinically healthy dogs.
ABSTRACT Thromboelastography (TEG) may be a valuable supplement to the coagulation assays activated partial thromboplastin time (aPTT), prothrombin time (PT), thrombin time (TT), fibrinogen, antithrombin (AT) and D-Dimer currently used in most clinical pathology laboratories. Allowable imprecision and bias reference limits for analytical tests can be calculated based on measurements of biological variation. No studies to date have examined the effect of biological variation on these haemostasis parameters in the same group of dogs. Plasma samples were collected after a set protocol once weekly for five consecutive weeks from eight healthy dogs (four males and four females) and stored at -80 degrees C until analysis. Randomized duplicate coagulation tests and TEG analyses were performed on all plasma samples within one run. The data were analyzed for outliers and subsequently subjected to nested analysis of variance to obtain the coefficient of analytical, intra-individual and inter-individual variation. From these objective analytical performance standards for imprecision, critical difference, total error and the index of individuality were calculated to assess the utility of conventional population-based reference ranges. All the clotting times (aPTT, PT and TT), fibrinogen, AT and D-Dimer showed a degree of individuality, which may make the use of population-based reference ranges alone an insensitive interpretation criterion, whereas a population-based reference interval seems to be sensitive for interpreting all TEG parameters. Analytical performance standards for imprecision were only met for one of the coagulation assays, whereas all TEG parameters except the alpha angle, alpha achieved this analytical goal.
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ABSTRACT: Previous studies have reported a strong correlation between indicators of red cell mass (RCM) and thromboelastometry results (TEM) in several species, specifically an association of apparent hypercoagulability with decreased RCM. The objectives of the study were to (1) evaluate the effect of decreased circulating RCM on TEM results in dogs, and (2) determine the relative contributions of citrate dilution vs in vivo reduction of RCM to hemostatic potential. Thirteen healthy dogs had one unit of blood removed on day 0. Whole blood, EDTA, and citrated blood samples for evaluation of TEM variables and PT, APTT, platelet count, fibrinogen, thrombin-antithrombin (TAT), and thrombin generation were collected at baseline, and 3 and 21 days after blood removal. Blood samples were also corrected to a PCV of 45% by adding citrate or removing plasma. On day 3 after blood removal, the PCV was significantly decreased (45 ± 6%) compared with baseline (52 ± 6%) and day 21 (50 ± 4%, P < .001), accompanied by TEM variables indicating hypercoagulability, which returned to baseline values by day 21. Other coagulation variables such as PT, APTT, platelet count, TAT, or plasma thrombin generation remained unchanged, with the exception of fibrinogen that was significantly higher on day 3. No changes were related to citrate dilution. Transiently decreased RCM in vivo was accompanied by TEM variables indicating hypercoagulability, which was not confirmed by other coagulation variables. This suggests an artifact of TEM, which presents a potential limitation of this technology in patient populations with abnormal RCM.Veterinary Clinical Pathology 03/2014; · 1.29 Impact Factor
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ABSTRACT: To systematically examine evidence surrounding definitions and reporting of data for viscoelastic testing in veterinary medicine. Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence and quality, and development of consensus on conclusions for application of the concepts to clinical practice. Academic and referral veterinary medical centers. Databases searched included Medline, CAB abstracts, and Google Scholar. All 4 standard thromboelastography (TEG) and rotational thromboelastometry (ROTEM) variables should be universally reported, and the reporting of shear elastic modulus in addition to maximum amplitude (MA) is encouraged. There is insufficient evidence to support universal usage of the coagulation index at this time. The K value and clot formation time are the most variable of the 4 parameters, with alpha angle, MA, and maximum clot firmness generally the least variable. Individual studies should report sufficient data on patients and institutional controls to enable definitions of hypo- and hypercoagulability to be evaluated post-hoc, and it is recommended that all studies specifically report how these conditions were defined. In reporting data relating to fibrinolysis, the TEG variables LY30, LY60, CL30, CL60, and the ROTEM variables LI30, LI60, ML, LOT, and LT should be documented. Studies should report sufficient data on patients and controls to enable definitions of hyper- and hypofibrinolysis to be evaluated post-hoc, and we suggest that standard TEG/ROTEM assays may be unable to detect hypofibrinolysis in companion animals. We recommend that every center establish reference intervals, which are specific to either TEG or ROTEM. These reference intervals should be established using veterinary clinical pathology guidelines, standardized protocols, and a minimum of 40 healthy animals. There are currently insufficient data in companion animals to suggest a utility for Vcurve variables beyond that of standard TEG variables.Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001). 01/2014; 24(1):47-56.
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ABSTRACT: Objective To characterize the overall hemostatic changes in dogs envenomated by crotaline snakes via kaolin-activated thromboelastography (TEG), and to determine any prognostic/monitoring value from a TEG tracing on presentation, as well as during treatment with antivenom therapy.DesignProspective observational, cohort study.SettingUniversity teaching hospital and primary emergency hospital.AnimalsThirty-eight dogs envenomated by crotaline snakes.InterventionsTEG tracings were evaluated on presentation to the hospital (pre) as well as immediately following (post) and 12 hours (12 h post) after antivenom treatment, if administered.Measurements and Main ResultsAt presentation, data were available for 38 dogs envenomated by crotaline snakes. Twenty dogs were in Group 1 (Antivenin [Crotalidae] Polyvalent antivenom), 12 dogs were in Group 2 (Antivipmyn antivenom), and 6 dogs in Group 3 that were not treated with antivenom. The average number of vials administered to group 1 and 2 were equal at 2.2. On presentation, based on a G value < TEG reference range, 15/38 (39%) of the dogs had hypocoagulable TEG tracings. There was a significant increase in G and MA value from the pre and 12 hour post measurement (P = 0.0001 and 0.0003, respectively), as well as from the post to 12 hour post measurement (P = 0.003 and, 0.014, respectively). During the study, 5 of 38 dogs died (13%) and of the dogs that died, 4/5 (80%) had angle and MA equal to zero on presentation. A decreased G and MA were significantly associated with mortality (P = 0.02 and 0.04, respectively).ConclusionsA hypocoagulable TEG tracing, particularly a decreased G value and MA, is associated with an increased mortality in crotaline snake envenomation. G and MA also demonstrate a significant increase over treatment time.Journal of Veterinary Emergency and Critical Care. 03/2014; 24(2).