One-stage prothrombin time, activated partial thromboplastin time, thrombin time, fibrin degradation product concentration, and antithrombin activity in healthy adult alpacas

Background: Alpacas are increasingly presented to veterinarians for evaluation and care. Reports of alpaca reference intervals for one‐stage prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), concentration of fibrin degradation products (FDP), and antithrombin (AT) activities are scarce or nonexistent. Objective: The aim of this study was to determine values for blood coagulation times (PT, aPTT, and TT), FDP concentrations, and AT activities in healthy adult alpacas. Methods: Of blood samples collected from 35 clinically healthy adult alpacas via jugular venipuncture and placed into sodium citrate and FDP tubes, 29 samples were assayable for coagulation testing. PT, aPTT, and TT were determined by physical (mechanical) clot detection; AT activity was determined using a thrombin‐specific chromogenic substrate end‐point assay; and FDP concentrations were determined by the slide agglutination method. Results: Median values and ranges (minimum–maximum) were determined for PT (8.7 seconds, 6.6–11.2 seconds), aPTT (17.3 seconds, 11.9–22.5 seconds), TT (10.2 seconds, 5.4–16.0 seconds), and AT activity (123.3%, 104.8–144.2%). The mean concentration of FDP was <8 μg/mL. Conclusion: These values for coagulation times, FDP concentration, and AT activity will provide a useful starting point in the diagnostic evaluation of ill adult alpacas.     

Effect of storage conditions on prothrombin time, activated partial thromboplastin time and fibrinogen concentration on canine plasma samples

The present study was to assess the effect of storage conditions on prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen concentration in blood samples of healthy dogs. Thirty-five dogs of various breeds were included in the study. Citrated blood samples were obtained and plasma was divided into four aliquots to assess selected clotting parameters by means of a coagulometer. The first aliquot was analysed within 1 h after collection, while the remaining 3 were stored at 8℃ for 4, 8 and 24 h, respectively. One-way repeated measures analysis of variance documented a significant decreasing effect on PT at 24 h compared to 8 h and on fibrinogen concentration after 8 and 24 h compared to sampling time and at 4 and 24 h compared to 8 h post sampling. In conclusion, the results of this study indicate that only fibrinogen appears prone to significant decrease. In fact, aPTT is not substantially affected by refrigeration for at least 24 h post sampling and PT showed a statistical difference that does not necessary indicate biological significance as the results obtained were within reference intervals for the dog.     

Prolonged activated prothromboplastin time and breed specific variation in haemostatic analytes in healthy adult Bernese Mountain dogs

Coagulation tests are often performed in dogs suspected of haemostatic dysfunction and are interpreted according to validated laboratory reference intervals (RIs). Breed specific RIs for haematological and biochemical analytes have previously been identified in Bernese Mountain dogs, but it remains to be determined if breed specific RIs are necessary for haemostasis tests. Activated prothromboplastin time (aPTT), prothrombin time (PT), selected coagulation factors, D-dimers, fibrinogen, von Willebrand factor and thromboelastography (TEG) were analyzed in healthy Bernese Mountain dogs using the CLSI model. Three analytes (aPTT, TEG [MA] and TEG [G]) were different according to the CLSI model. For aPTT the new RI was markedly different (0-100s). Whereas the new intervals for TEG (MA) and TEG (G) may be due to breed related biological variation, the cause of the prolonged RI for aPTT is at present uncertain.     

Comparison of prothrombin time, activated partial thromboplastin time, and fibrinogen concentration in blood samples collected via an intravenous catheter versus direct venipuncture in dogs

OBJECTIVE: To compare prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration in canine blood samples collected via an indwelling IV catheter and direct venipuncture. ANIMALS: 35 dogs admitted to an intensive care unit that required placement of an IV catheter for treatment. PROCEDURES: Blood samples were collected via IV catheter and direct venipuncture at the time of catheter placement and 24 hours after catheter placement. Prothrombin time, APTT, and fibrinogen concentration were measured. RESULTS: 5 dogs were excluded from the study; results were obtained for the remaining 30 dogs. Agreement (bias) for PT was -0.327 seconds (limits of agreement, -1.350 to 0.696 seconds) and 0.003 seconds (limits of agreement, -1.120 to 1.127 seconds) for the 0- and 24-hour time points, respectively. Agreement for APTT was -0.423 seconds (limits of agreement, -3.123 to 2.276 seconds) and 0.677 seconds (limits of agreement, -3.854 to 5.207 seconds) for the 0- and 24-hour time points, respectively. Agreement for fibrinogen concentration was -2.333 mg/dL (limits of agreement, -80.639 to 75.973 mg/dL) and -1.767 mg/dL (limits of agreement, -50.056 to 46.523 mg/dL) for the 0- and 24-hour time points, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Agreement between the 2 techniques for sample collection was clinically acceptable for PT, APTT, and fibrinogen concentration at time 0 and 24 hours. It is often difficult or undesirable to perform multiple direct venipunctures in critically ill patients. Use of samples collected via an IV catheter to monitor PT and APTT can eliminate additional venous trauma and patient discomfort and reduce the volume of blood collected from these compromised patients.     

Diagnosis of disseminated intravascular coagulation in dogs admitted to an intensive care unit.

OBJECTIVE: To describe and evaluate hemostatic function in critically ill dogs with clinical signs of diseases that predispose to disseminated intravascular coagulation (DIC). DESIGN: Prospective case series. ANIMALS: 59 critically ill dogs (affected dogs) with clinical signs of diseases known to predispose to DIC and 52 clinically normal dogs (control dogs). PROCEDURE: Activated partial thromboplastin time (aPTT), prothrombin time (PT), thrombin clotting time (TCT), plasma fibrinogen concentration, serum concentration of fibrin and fibrinogen-related antigens (FRA), and plasma antithrombin III (AT III) activity were determined for all dogs. Results from affected dogs were compared with those of control dogs. In some affected dogs, postmortem tissue specimens were examined for evidence of microvascular thrombosis. A diagnosis of DIC was made by fulfilling at least 3 of the following criteria: 1) abnormal aPTT, PT, or TCT value, 2) low plasma fibrinogen concentration, 3) low plasma AT III activity, 4) high serum FRA concentration, or 5) low platelet count. To evaluate the severity of hemostatic dysfunction, 3 arbitrary categories (mild, moderate, and severe) were proposed. RESULTS: A diagnostic strategy based on moderate hemostatic dysfunction identified DIC in 16 of 59 (27.1%) affected dogs. The AT III activity was < 70% in 15 of 16 dogs with DIC. Microvascular thrombosis was observed in tissue specimens from 7 of 8 affected dogs. Serum FRA and plasma fibrinogen concentrations did not contribute in establishing a diagnosis of DIC. CONCLUSIONS AND CLINICAL RELEVANCE: A diagnosis of DIC can be made when hemostatic dysfunction is moderate in dogs with clinical signs of diseases associated with DIC.     

Coagulation values in normal ferrets (Mustela putorius furo) using selected methods and reagents

Background: Accurate determination of commonly measured coagulation values would be useful in the diagnosis and management of coagulopathies in domestic ferrets (Mustela putorius furo). We are unaware of reports of coagulation times in this species. Objectives: The purpose of this study was to determine reference values for prothrombin time (PT), activated partial thromboplastin time (PTT), fibrinogen concentration, and antithrombin (AT) activity in ferrets using selected methods and reagents. Methods: Blood samples obtained from 18 clinically healthy ferrets were anticoagulated with 0.129 M sodium citrate in a ratio of 9 parts blood to 1 part anticoagulant. Plasma was collected and stored at -70 degrees C until analysis. PT and PTT were measured with a fibrometer and with an ACL 3000 automated system. PTT was measured with and without the addition of ellagic acid. Fibrinogen was assayed by a turbidimetric method. AT activity was determined using a chromogenic assay and pooled ferret plasma (100% activity). Differences in methods and reagents were evaluated using paired t tests. Results: PT was significantly longer using the fibrometer (12.3+/-0.3, 11.6-12.7 seconds) compared with the ACL (10.9+/-0.3, 10.6-11.6 seconds) (P<.01). PTT was not significantly different with the fibrometer (18.7+/-0.9, 17.5-21.1 seconds) vs the ACL (18.1+/-1.1, 16.5-20.5 seconds), but was significantly longer on both analyzers when ellagic acid was added (fibrometer 20.4+/-0.8, 18.9-22.3 seconds; ACL 20.0+/-1.0, 18.6-22.1 seconds) (P<.01). Fibrinogen concentration was 107.4+/-19.8 mg/dL (90.0-163.5 mg/dL), and AT activity was 96%+/-12.7% (69.3-115.3%). Conclusion: These coagulation results for healthy ferrets will be useful in the evaluation of ferrets with coagulopathies, provided similar reagents and methods are used.     

Effect of citrate concentration on coagulation test results in dogs

OBJECTIVE: To determine the effect of citrate concentration (3.2 vs 3.8%) on coagulation tests in dogs. DESIGN: Original study. ANIMALS: 30 clinically healthy dogs and 12 dogs with hereditary hemostatic disorders. PROCEDURE: Blood was collected from all dogs directly into collection tubes containing 3.2 or 3.8% buffered citrate. Prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen concentration were measured by use of 3 clot-detection assay systems (2 mechanical and 1 photo-optic). Factor VIII and factor IX coagulant activities (FVIII:C and FIX:C, respectively) were determined by use of a manual tilt-tube method and a mechanical clot-detection device. RESULTS: Significant differences were not detected in median PT, fibrinogen concentration, FVIII:C, or FIX:C between 3.2 and 3.8% citrate for any assay system. A significant prolongation in aPTT for 3.2% citrate, compared with 3.8% citrate, was found in 1 mechanical system. CONCLUSIONS AND CLINICAL RELEVANCE: Citrate concentration does not significantly affect results of most coagulation assays, regardless of assay system. The aPTT was mildly influenced by the citrate concentration, although this was animal-, instrument-, and reagent-dependent. The choice of 3.2 or 3.8% citrate as an anticoagulant for coagulation tests has minimal influence on assay results in healthy dogs or dogs with hereditary hemostatic disorders.     

Prothrombin time and activated partial thromboplastin time using a point‐of‐care analyser (Abaxis VSpro®) in Bennett's wallabies (Macropus rufogriseus)

There are few reports of coagulation times in marsupial species. Blood samples collected from 14 Bennett's wallabies (Macropus rufogriseus) under anaesthesia during routine health assessments were analysed for prothrombin time (PT) and activated partial thromboplastin time (aPTT) using a point‐of‐care analyser (POC) (Abaxis VSPro®). The wallabies had an aPTT mean of 78.09 s and median of 78.1 s. The PT for all wallabies was greater than 35 s, exceeding the longest time measured on the POC. Although PT was significantly longer, aPTT was similar to the manufacturer's domestic canine reference range.     

Effects of 2 concentrations of sodium citrate on coagulation test results, von Willebrand factor concentration, and platelet function in dogs

BACKGROUND: Blood collection tubes containing 3.2% (0.109 M) sodium citrate, instead of 3.8% (0.129 M) sodium citrate, have recently become available in the United States. These tubes are visually indistinguishable from the traditional 3.8% sodium citrate tubes, except for wording on the label. Consequently, samples for hemostatic evaluation are frequently collected in tubes containing the lower concentration of sodium citrate. HYPOTHESIS: Results of hemostasis assays are different in samples collected in 3.2% versus 3.8% sodium citrate. ANIMALS: Twenty healthy dogs. METHODS: This study aimed at determining whether results of standard coagulation tests, von Willebrand factor concentration (vWF:Ag), and platelet function with the platelet function analyzer PFA-100a were affected by the different concentrations of sodium citrate. Blood samples were collected in tubes containing either 3.2% or 3.8% sodium citrate concentrations and processed routinely for coagulation assays (one-stage prothrombin time [OSPT], activated partial thromboplastin time [aPTT], fibrinogen concentration, and platelet count), vWF:Ag, and platelet function assays with a PFA-100. RESULTS: There was no significant difference between samples collected in 3.2% versus those collected in 3.8% sodium citrate for OSPT, aPTT, fibrinogen concentration, platelet count, or vWF:Ag. The closure times with collagen/adenosine diphosphate were significantly shorter (66 +/- 8.1 versus 74.8 +/- 9.7 seconds; P < .0001) with the 3.2% than with 3.8% sodium citrate concentration, and the hematocrit was significantly higher (47.9 +/- 5.6 versus 46.0 +/- 4.7 seconds; P = .03) in samples collected in 3.2% than in those collected in 3.8% sodium citrate. CONCLUSIONS AND CLINICAL IMPORTANCE: There is no clinically relevant effect of collection of blood into 3.2% or 3.8% sodium citrate.     

Pharmacokinetics and pharmacodynamics of a therapeutic dose of unfractionated heparin (200 U/kg) administered subcutaneously or intravenously to healthy dogs

BACKGROUND: Heparin treatment has been recommended for dogs in hypercoagulable states such as disseminated intravascular coagulation, however, potential benefits have to be balanced against the bleeding risk if overdosage occurs. A better understanding of the pharmacology of heparin and tests to monitor heparin therapy in dogs may help prevent therapeutic hazards. OBJECTIVES: The purpose of this study was to evaluate the effects of 200 U/kg of sodium unfractionated heparin (UFH) on coagulation times in dogs after intravenous (IV) and subcutaneous (SC) administration and to compare these effects with plasma heparin concentrations assessed by its antifactor Xa (aXa) activity. METHODS: 200 U/kg of UFH were administered IV and SC to 5 healthy adult Beagle dogs with a washout period of at least 3 days. Activated partial thromboplastin time (APTT), prothrombin time (PT), and plasma aXa activity were determined in serial blood samples. RESULTS: After IV injection, PT remained unchanged except for a slight increase in 1 dog; APTT was not measurable (>60 seconds) for 45-90 minutes, and then decreased gradually to baseline values between 150 and 240 minutes. High plasma heparin concentrations were observed (maximal concentration = 4.64 +/-1.4 aXa U/mL) and decreased according to a slightly concave-convex pattern on a semilogarithmic curve, but returned to baseline slightly more slowly (t240-t300 minutes) than did APTT. After SC administration, APTT was moderately prolonged (by a ratio of 1.55 +/-0.28 APTT t0, range 1.35-2.01) between 1 and 4 hours after administration. Plasma aXa activity reached a maximum of 0.56 +/-0.20 aXa U/mL (range 0.42-0.9 U/mL) after 132 +/-26.8 minutes; this lasted for 102 +/-26.8 minutes. Prolongation of APTTs of 120-160% corresponded to plasma heparin concentrations of 0.3-0.7 aXa U/mL. CONCLUSIONS: As in humans, the pharmacokinetics of UFH in dogs was nonlinear. Administration of 200 U/kg of UFH SC in healthy dogs resulted in sustained plasma heparin concentrations in accordance with human recommendations for thrombosis treatment or prevention, without excessively increased bleeding risks. In these conditions, APTT can be used as a surrogate to assess plasma heparin concentrations. These findings need to be confirmed in diseased animals.     

Relationship between assays of inflammation and coagulation: A novel interpretation of the canine activated clotting time

The processes of inflammation and coagulation are known to be interconnected through several mechanisms; however, the influence of inflammation on the interpretation of coagulation assays remains unknown. Blood was collected from 87 dogs admitted to a tertiary referral intensive care unit (ICU) and 15 control dogs. The association between 2 markers of inflammation [mature neutrophil count and C-reactive protein (CRP)] and 5 coagulation parameters [activated clotting time (ACT), prothrombin time (PT), activated partial thromboplastin time (aPTT), antithrombin (AT), and platelet count (plt)] were evaluated through correlation analysis. The study population was then divided into 4 groups based on severity of ACT prolongation with comparisons to all other variables assessed through an analysis of variance (ANOVA) test. A strong correlation for a biological system was demonstrated between ACT and CRP (r = 0.66; P < 0.0001). Statistically significant results were also found between aPTT and AT with the markers of inflammation, but the correlations were weaker. Within ACT groups of increasing severity, higher CRP concentrations (P < 0.0001) and lower AT activities (P < 0.0001) were identified. This study provides evidence for an association between assays of inflammation and coagulation and suggests that modification of our traditional interpretations of coagulation assays may be required. As a point-of-care test, ACT is a simple and inexpensive tool that can be used to assess an underlying inflammatory or hemostatic process.     

Clotting profiles in newborn maltese kids during the first week of life.

The neonatal period is probably the only time when a higher incidence of spontaneous thromboembolic complications may occur in the otherwise normal, healthy individual. This study was designed to determine the postnatal development of the kid coagulation system. Ten clinically healthy and full-term-born Maltese kid goats (5 males and 5 females) were used. In each kid, during the first week after birth, the prothrombin time (PT), the activated partial thromboplastin time (aPTT), the thrombin time (TT), and fibrinogen were assessed. Analysis of variance showed a highly significant effect of age on PT, TT, and fibrinogen. Our results of this study indicate that the clotting mechanism in kids is influenced by growth. This investigation contributes to the knowledge of clotting adaptations in kids during the first 7 days of life and provides useful information for the diagnosis and treatment of some neonatal diseases.     

Measurement of prothrombin time (PT) and activated partial thromboplastin time (APTT) on canine citrated plasma samples following different storage conditions

Samples from 75 clinically ill dogs were utilised in the study. APTT and PT tests were performed immediately on fresh citrated plasma samples (Fresh). The remaining plasma was stored at -20 degrees C for less than 4 months (n=36 samples) or between 4 and 7 months (n=39 samples). In batches of five, frozen samples were thawed rapidly and APTT and PT tests were performed on the thawed samples immediately (0RT) and after storage at room temperature (23 degrees C, range: 22-25 degrees C) for 24h (24RT) and 48h (48RT). The median APTT value from the (0RT) samples was significantly longer than that obtained from fresh samples (15s vs. 13.2s) but the PT value was not statistically different (7.8s vs. 7.6s). The median APTT (15s) and PT (7.5s) results from the (24RT) samples were not statistically different to those from the (0RT) samples (APTT: 15s, PT: 7.6s) but both tests were significantly longer (APTT: 16.5s, PT: 9.2s) from the (48RT) samples. We concluded that long term batching and freezing of clinical samples at -20 degrees C is acceptable for measurement of PT but not of APTT. We demonstrated that APTT and PT results do not change following storage of samples at room temperature for 24h but storage for 48h may lead to statistically and clinically significant changes (values at least 25% higher than the high value of the laboratory's reference interval) in both clotting times.     

Prothrombin, activated partial thromboplastin, and proteins induced by vitamin K absence or antagonists clotting times in 20 hyperthyroid cats before and after methimazole treatment

The effect of daily doses of 5-15 mg of methimazole on the platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), and proteins induced by vitamin K absence or antagonists (PIVKA) clotting time in 20 hyperthyroid cats was determined. No significant (P > .05) difference was found in median platelet count. PT, APTT, or PIVKA clotting time before treatment compared to median values at 2-6 weeks or > or =7-12 weeks of methimazole treatment. No cat had a prolonged APTT at any time. At 2-6 weeks of methimazole treatment, 1 cat each developed thrombocytopenia or prolonged PIVKA clotting time despite initially normal values. Three cats had abnormal coagulation tests (prolonged PT [n = 1] and PIVKA clotting time [n = 3]) before treatment that fluctuated during treatment. Excluding the 3 cats that had abnormal PIVKA clotting time before treatment, prolonged PIVKA clotting time developed in 6% (1/17; 95% confidence interval, 0-28%) cats treated with methimazole for 2-6 weeks. Seemingly. doses of methimazole commonly used to treat hyperthyroidism in cats do not cause alteration in PT and APTT, and only rarely prolong PIVKA clotting time. Nevertheless, abnormal PIVKA clotting time may explain bleeding tendencies unassociated with thrombocytopenia in methimazole-treated hyperthyroid cats.     

An evaluation of activated coagulation time in warfarin-intoxicated dogs

Activated coagulation time, one stage prothrombin time and activated partial thromboplastin time were compared in warfarin-intoxicated dogs. All coagulation tests were significantly prolonged on the third and fourth days following intoxication. Coagulation assays of all dogs except one returned to preintoxication values one day following vitamin K therapy. Significant correlation was found between all coagulation tests in the intoxicated group. Activated coagulation time may provide a useful coagulation screening test to veterinarians with limited laboratory capabilities.     

Artifactual Prolongation of the Activated Partial Thromboplastin Time Associated With Hemoconcentration in Dogs

An inappropriate blood-to-anticoagulant ratio can cause an artifactual prolongation of the activated partial thromboplastin time (APTT) and prothrombin time (PT). In a drug safety study in dogs, we observed a 4-to 5-second increase in the APTT from baseline coincident with increased hematocrit values (56% to 65%) secondary to drug-induced vomiting and diarrhea. The PT and platelet counts were unchanged, and there was no clinical evidence of bleeding associated with venipuncture. Although we were unable to sample the same dogs to investigate the possible effect of hemoconcentration on the prolonged APTT, the question was addressed by an in vitro study. The hematocrit value for citrated blood samples collected from healthy beagle dogs was increased by the addition of aliquots of red blood cell/plasma mixtures in vitro while maintaining a 9:1 blood-to-anticoagulant ratio. There was a 2-to 4-second prolongation of the APTT associated with hematocrit values of 55% to 61 %, but the PT was not prolonged. Adjustment of the blood-to-anticoagulant ratio corrected the prolongation. This study emphasizes the important relationship of the blood-to-anticoagulant ratio when measuring coagulation tests in hemoconcentrated samples.     

Stability of stored canine plasma for hemostasis testing

BACKGROUND: A review of the literature revealed limited information about the stability of samples for coagulation testing in dogs. OBJECTIVE: The aim of this study was to evaluate the stability of individual coagulation factors, clotting times, and other parameters of hemostasis in stored canine plasma. METHODS: Citrated plasma samples were obtained from 21 dogs. Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration, and factor I, II, V, VII, VIII, IX, X, XI, and XII activities were measured on an automated coagulation analyzer with commercially available reagents. Antithrombin (AT) activity and D-dimer concentration were measured on an automated chemistry analyzer using validated kits. Samples were analyzed within 1 hour after collection (initial analysis) and once daily for 2 or 4 consecutive days following storage at room temperature (RT) or 4 degrees C, respectively. RESULTS: Storage time at either temperature did not have any effect on PT, factor II, V, VII, X, or XII activities, D-dimer concentration, or AT activity. In contrast, aPTT was significantly prolonged after 72 and 96 hours at 4 degrees C; fibrinogen concentration was decreased after 48 hours at RT; the activities of factors VIII and IX were decreased after 48, 72, and 96 hours at 4 degrees C; and factor XI activity was decreased after 72 hours at 4 degrees C. CONCLUSIONS: Results suggest that storage of canine plasma for 2 days at RT does not have a significant effect on hemostasis test results with the exception of a slight decrease in fibrinogen concentration. In contrast, aPTT and factors VIII, IX, and XI were unstable in refrigerated plasma after 48 or 72 hours of storage.     

Study on biological variation of haemostatic parameters in clinically healthy dogs

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.     

Thromboelastographic tracings in retired racing greyhounds and in non-greyhound dogs

BACKGROUND: Bleeding disorders in patients with normal coagulation test results are frequently reported in Greyhounds. The purpose of this study was to compare Greyhounds to non-Greyhounds by thromboelastography (TEG). HYPOTHESIS: TEG parameters in Greyhounds are different from those in non-Greyhounds. ANIMALS: Forty-three healthy dogs (28 Greyhounds and 15 non-Greyhounds) based on the results of physical examination, CBC, activated partial thromboplastin time, prothrombin time, fibrinogen, and platelet count. MATERIALS AND METHODS: Recalcified citrated native TEGs were performed in both groups; data were compared using Student's, Mann-Whitney, and Pearson's statistical tests. RESULTS: In Greyhounds, mean +/- SD were as follows: R-time 4.3 +/- 1.7 minutes, K-time 3.8 +/- 1.4 minutes, angle (alpha) 50.0 +/- 8.0 degrees , maximum amplitude (MA) 47.6 +/- 5.6 mm, clot strength (G) 4,647 +/- 1,097 dyn/cm2, and percent lysis at 60 minutes (LY60) 2.8 +/- 5.0%. In the non-Greyhounds they were R-time 3.7 +/- 1.6 minutes, K-time 2.5 +/- 0.9 minutes, angle 59.8 +/- 7.0 degrees , MA 53.1 +/- 5.6 mm, G 5,811 +/- 1,256 dyn/cm2, and LY60 3.1 +/- 2.5%. All parameters were significantly different between the groups, except for R-time and LY60. CONCLUSION: In Greyhounds, clotting kinetics are slower and clot strength are weaker than in non-Greyhounds, supporting the increased tendency to bleed observed after minor trauma or surgical procedures in the breed. The findings may also be attributed to blood viscosity or to the concentration of citrate in the sample (ie, Greyhounds have higher hematocrit and less plasma per unit volume).     

Evaluation of a bench-top coagulation analyzer for measurement of prothrombin time, activated partial thromboplastin time, and fibrinogen concentrations in healthy dogs

OBJECTIVE: To evaluate a bench-top coagulation analyzer for determination of prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration in healthy dogs. ANIMALS: 55 healthy adult dogs. PROCEDURES: PT, APTT, and fibrinogen concentration were determined by use of the coagulation analyzer. Values were compared with results obtained independently by a conventional laboratory. RESULTS: Correlations (with 95% confidence intervals) between the coagulation analyzer and conventional laboratory values were 0.760 (0.610 to 0.857), 0.700 (0.448 to 0.721), and 0.896 (0.878 to 0.918) for PT, APTT, and fibrinogen concentration, respectively. Using linear regression, comparison of data from the coagulation analyzer and the conventional laboratory provided equations relating the coagulation analyzer values with values from the conventional laboratory and suggested that APTT and fibrinogen values from the coagulation analyzer and conventional laboratory were approximately the same within expected random variation. Prothrombin time values for the coagulation analyzer were significantly offset from the PT values for the conventional laboratory but still were correlated reasonably well with the conventional laboratory values. CONCLUSIONS AND CLINICAL RELEVANCE: By use of the mechanical method of analysis, fibrinogen concentrations obtained with a bench-top coagulation analyzer correlated well with results for a conventional laboratory, indicating that the coagulation analyzer is a reliable instrument for determination of this coagulation variable. Coagulation analyzer results for PT and APTT correlated less strongly with those for the conventional laboratory, but they would still be considered clinically reliable.