Glanzmann thrombasthenia in a 17-year-old Peruvian Paso mare

A 17-year-old Peruvian Paso mare was evaluated for bilateral epistaxis that had been present for at least 3 years. The mare had mild anemia, platelet count within the reference interval, unremarkable coagulation times, and a negative Coggins test. On endoscopic examination, structural abnormalities were not observed in the nasal cavities, pharynx, larynx, trachea, or either guttural pouch, but petechiation was noted in the nasal mucosa. Additional tests revealed prolonged cutaneous bleeding time, normal concentration of von Willebrand factor antigen, an abnormal clot retraction test, and failure of plalelet aggregation in response to agonists, suggesting a functional disorder of platelets. Genetic analysis indicated the horse was homozygous for a 10-base-pair deletion that included the last 3 base pairs of exon 11 and the first 7 base pairs of intron 11 of the gene encoding glycoprotein IIb. The diagnosis was Glanzmann thrombasthenia (GT) caused by a structural defect in glycoprotein IIb. GT is an autosomal recessive disorder caused by a defect in the glycoprotein IIb-IIIa complex on platelet surfaces. Separate genes encode each glycoprotein, and mutations in either gene can result in GT. This case of GT is unique given the age of the mare at the time of diagnosis. We conclude that GT, although an inherited disorder, should be considered in horses with suspected dysfunctional platelets, regardless of age.     

Thrombelastography in 26 healthy horses with and without activation by recombinant human tissue factor

Objectives – To develop a standardized technique for thrombelastography (TEG) analysis in healthy adult horses, with and without the ex vivo addition of tissue factor (TF) as an activator. To determine reference intervals for TEG parameters in the horse, and to determine if traditional coagulation tests correlate with TEG. Design – Prospective, observational. Setting – Veterinary teaching hospital. Animals – Twenty‐six healthy adult horses. Interventions – None. Measurements and Main Results – Thrombelastography with (TF‐TEG) and without (TEG) the addition of TF performed by 4 operators. Coagulation profiles (prothrombin time, activated partial thromboplastin time, platelet count, fibrinogen, antithrombin, and fibrinogen degradation products) were assessed in a subset of horses. Mean values (SD) for TEG parameters in healthy horses were: reaction time (R)=17.0 minutes (3.0 min), K time (K)=5.8 minutes (2.3 min), clotting rate (Ang)=42° (14°), maximum clot strength (maximum amplitude [MA])=60.3 mm (5.7 mm), CL30=97.0% (2.0%), LY30=0.8% (0.6%), CL60=92% (5.9%), LY60=3.2% (2.5%). Mean values (SD) for TF‐TEG parameters were: R‐TF=6.6 minutes (1.4 min), K‐TF=3.1 minutes (1.0 min), Ang‐TF=50.9° (9°), MA‐TF=62.3 mm (5.1 mm), CL30‐TF=97.8% (1.6%), LY30‐TF=0.6% (0.5%), CL60‐TF=90.8% (4.2%), and LY60‐TF=3.6% (1.9%). The addition of TF decreased R and K and increased Ang. TF‐TEG had a narrower SD for R, K, Ang, CL60 and LY60 compared with TEG. Interoperator differences were reduced by the addition of TF. Regression analysis indicated a positive relationship between MA and fibrinogen concentrations (P=0.02) and R‐TF time and prothrombin time (P=0.03). Conclusion – TF‐TEG using the described protocol may minimize variability in data obtained across institutions or users. However, due to the variability associated with different operators, it is recommended that each laboratory set up individual reference intervals with the personnel who will perform the assay, and that the assay protocols and data obtained are compared on a regular basis.     

Thromboelastographic changes after gonadectomy in retired racing greyhounds

Twenty-one healthy greyhounds with no history or clinical signs of bleeding disorders, and no abnormalities on physical examination, complete blood count, serum biochemistry profiles (in dogs more than five years of age), and SNAP-4DX test for vector borne diseases underwent routine gonadectomies at the Ohio State University Veterinary Teaching Hospital. Blood samples were collected 24 hours before and after surgery by jugular venepuncture for thromboelastography and haemostasis assays (prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration). The magnitude of the bleeding in each patient was estimated using a bleeding scoring system recently validated in greyhounds. Eight dogs were classified as bleeders and 13 as non-bleeders. Thromboelastograph (TEG) tracings in bleeders were different to that of non-bleeders. Neither sex (odds ratio [OR]: 0.148, P=0.05), haematocrit (OR: 0.907, P=0.39), platelet count (OR: 0.996, P=0.65) or age (OR: 0.949, P=0.83) were predictors of the outcome. None of the variables that evaluated clot kinetics, and fibrinolysis (that is, aPTT OR: 0.781, P=0.51; PT OR: 1.337, P=0.63; TEG(R) OR: 1.269, P=0.06; TEG(K) OR: 1.696, P=0.05; TEG(LY60) OR: 1.028, P=0.81) were able to predict the bleeding episodes. Only the TEG variables that represent the fibrin cross-linking of the clot (TEG(angle) OR: 0.903, P=0.03); and the strength of the clot (TEG(MA) OR: 0.833, P=0.03) were considered predictors of the outcome.     

Preliminary studies of a platelet function disorder in Simmental cattle.

A bleeding disorder due to abnormal platelet function occurs in Simmental cattle. Whole blood from these animals underwent good clot retraction. Platelet aggregation in response to adenosine diphosphate (ADP) and collagen in a whole blood aggregation system was markedly impaired. Normal bovine platelets in a whole blood aggregation system showed very little aggregation in response to epinephrine and arachidonic acid. Aggregation in platelet-rich plasma was negligible in response to ADP, collagen and thrombin. Dense granule release of radiolabelled serotonin from the platelets of one affected cow was similar to that of normal bovine platelets. Platelet membrane glycoprotein electrophoresis with the platelets of one affected cow revealed no quantitative abnormalities. These findings reveal similarities and differences in thrombopathic Simmental platelet function when compared to human Glanzmann's thrombasthenia and Basset Hound thrombopathia.     

Molecular and genetic basis for thrombasthenic thrombopathia in otterhounds.

OBJECTIVES: To determine the molecular and genetic basis for thrombasthenic thrombopathia in Otterhounds and establish whether the defect would be best classified as type-I Glanzmann's thrombasthenia. ANIMALS: 57 dogs, including 13 affected Otterhounds, 23 carrier Otterhounds, 17 unaffected Otterhounds, and 4 clinically normal unrelated dogs of other breeds. PROCEDURE: Functional (platelet aggregation, clot retraction, buccal mucosa bleeding time) and biochemical (electrophoresis, flow cytometry, fibrinogen content) analyses were conducted. In addition, first-strand cDNA synthesis from platelet total RNA was performed. Exons of the genes encoding for glycoproteins (GP) IIb and IIIa were amplified in overlapping fashion. The resulting products were excised from agarose gels and sequenced. The sequences obtained were compared with known cDNA sequences for canine GPIIb and GPIIIa. RESULTS: A single nucleotide change at position G1193 (1100) was detected in exon 12 of the gene encoding for platelet GPIIb in 2 affected Otterhounds. Carrier Otterhounds were heterozygous at this position, and 2 unaffected Otterhounds were unchanged. This nucleotide change would result in substitution of histidine for aspartic acid at position 398 (367) within the third calcium-binding domain of GPIIb. CONCLUSIONS AND CLINICAL RELEVANCE: These studies suggest that thrombasthenic thrombopathia of Otterhounds is homologous phenotypically and has a similar molecular basis to type-I Glanzmann's thrombasthenia in humans.     

Thrombopathies causing bleeding in a boxer and mixed-breed dog

Hereditary platelet function disorders are clinically characterized by recurrent surface bleeding and prolonged bleeding time, despite normal platelet count and coagulation tests. The authors describe persistent thrombopathies in two young dogs with increased bleeding tendencies but with normal plasma coagulation times and von Willebrand factor (vWf) concentrations. Buccal mucosal bleeding times were prolonged in both dogs. In aggregation studies, platelets underwent only a shape change or minimal aggregation in response to adenosine diphosphate and collagen. Whole-platelet adenine nucleotide concentrations were normal. Electron microscopic evaluation of fibrinogen and vWf binding to the platelets of case no. 1 demonstrated the presence of glycoprotein IIb/IIIa and Ib receptors. Thus, the intrinsic platelet function defects may be different in these two dogs and may likely represent secretion/signal transduction disorders.     

Evaluation of platelet function screening tests to detect platelet procoagulant deficiency in dogs with Scott syndrome

Background: Clinical diagnosis of platelet dysfunction is complex and technically challenging. The wide repertoire of platelet responses requires a test panel to assess different parameters of platelet reactivity. While “global” hemostasis analyzers and whole blood assays have potential for testing platelet function, their ability to evaluate platelet procoagulant activity is ill‐defined. Objectives: The aim of this study was to determine whether platelet procoagulant deficiency, the pathophysiologic defect of Scott syndrome, could be detected in point‐of‐care and whole blood assays. Methods: Study subjects were 4 Scott syndrome‐affected German Shepherds and 8 control dogs. We evaluated 2 point‐of‐care instruments: the platelet function analyzer (PFA‐100) and thromboelastograph (TEG). TEG analysis was performed on recalcified citrated whole blood with and without tissue‐factor activation. A whole blood flow cytometric assay was configured to detect thrombin‐induced platelet P‐selectin expression and platelet‐derived microparticle release. Cytometric samples were analyzed after 1 hour and 1 day of storage. Results: We found no significant differences between Scott and control dogs in PFA‐100 COL/ADP closure times or in any TEG parameter in tissue‐factor–activated samples. In nonactivated samples, mean clotting time (K) and time to maximal rate of thrombus generation were significantly prolonged in Scott dogs; however, values overlapped with those of control dogs. Cytometric analysis of samples from Scott dogs showed significantly diminished platelet‐derived microparticle release. Samples from all dogs reanalyzed after 1 day of storage had nonspecific increases in basal P‐selectin expression and vesiculation. Conclusion: A whole blood cytometric assay to detect stimulated platelet microparticle release can be used to screen for Scott syndrome. However, platelet activation artifacts preclude overnight storage for next‐day analysis.     

Thromboelastography results on citrated whole blood from clinically healthy cats depend on modes of activation

Background

During the last decade, thromboelastography (TEG) has gained increasing acceptance as a diagnostic test in veterinary medicine for evaluation of haemostasis in dogs, however the use of TEG in cats has to date only been described in one previous study and a few abstracts. The objective of the present study was to evaluate and compare three different TEG assays in healthy cats, in order to establish which assay may be best suited for TEG analyses in cats.

Methods

90 TEG analyses were performed on citrated whole blood samples from 15 clinically healthy cats using assays without activator (native) or with human recombinant tissue factor (TF) or kaolin as activators. Results for reaction time (R), clotting time (K), angle (α), maximum amplitude (MA) and clot lysis (LY30; LY60) were recorded.

Results

Coefficients of variation (CVs) were highest in the native assay and comparable in TF and kaolin activated assays. Significant differences were observed between native and kaolin assays for all measured parameters, between kaolin and TF for all measured parameters except LY60 and between native and TF assays for R and K.

Conclusion

The results indicate that TEG is a reproducible method for evaluation of haemostasis in clinically healthy cats. However, the three assays cannot be used interchangeably and the kaolin- and TF activated assays have the lowest analytical variation indicating that using an activator may be superior for performing TEG in cats.     

Thrombelastography in dogs admitted to an intensive care unit

Background: Underlying conditions in dogs admitted to an intensive care unit (ICU) can cause hemostatic dysfunction. Thrombelastography (TEG) may be useful in detecting hemostatic alterations as compared with standard coagulation tests. Objectives: The purpose of this study was to compare TEG results and those of standard coagulation tests in identifying hemostatic dysfunction in dogs admitted to an ICU and to investigate associations among the variables measured. Methods: Tissue factor‐activated TEG analysis, d ‐dimer and fibrinogen concentrations, antithrombin (AT) activity, prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count were measured using standard techniques on 27 dogs admitted to ICU with a disease known to be associated with hemostatic dysfunction and in 31 clinically healthy control dogs. Results were compared between groups using nonparametric tests and κ analysis; principal component analysis (PCA) and Spearman rank correlation were used to measure associations among variables. Results: Fourteen of 27 ICU dogs had abnormal TEG tracings, which were used to classify the dogs as hypercoagulable (n=11), hypocoagulable (n=3), or normocoagulable (n=13). Hypercoagulable dogs had significantly increased d ‐dimer (P=.03) and fibrinogen (P=.01) concentrations compared with normocoagulable dogs. In ICU dogs, positive associations were identified between maximum amplitude (MA), α‐angle, fibrinogen concentration, and platelet count, and between PT, aPTT, and reaction time (R). Significant correlations were found between MA and fibrinogen (r_s=.76, P<.001) and between reaction time (R) and PT (r_s=.51, P=.003). Conclusions: TEG was useful in detecting hemostatic dysfunction in dogs in an ICU. Positive associations among variables may provide insight as to how overall coagulation status reflects alterations in clot strength and coagulation time. Dogs with TEG tracings indicative of hypercoagulability are likely in procoagulant states. Future studies of the incidence of thrombotic complications in dogs with hypercoagulable TEG tracings are warranted.     

Hemostatic abnormalities in dogs with carcinoma: a thromboelastographic characterization of hypercoagulability

Hemostatic abnormalities were investigated in 32 dogs with carcinoma and 19 age-matched healthy dogs. Thromboelastography, hemostasis profile (i.e. prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration), platelet count (PLT), thrombin-antithrombin complexes (TAT), and plasminogen activator inhibitor-1 (PAI-1) activity were evaluated. Dogs with carcinomas had faster thrombus generation (TEG(TG), a mathematic value obtained from the first derivate of the thromboelastographic tracing; 834.8±91.1 vs. 707.8±75.8mm/min; mean±SD), increased fibrinogen concentration (276 vs. 151mg/dL), and PLT (425 vs. 324U×10(9)/L), but had decreased PAI-1 activity (15.7 vs. 26.2IU/mL).The most common hemostatic abnormalities found in carcinoma dogs were hypercoagulability (TEG(TG)>mean+2 SD of healthy dogs) and thrombocytosis (PLT>424×10(9)U/L) in 46% of cases, and hyperfibrinogenemia (fibrinogen >384mg/dL) in 32% of cases. Disseminated intravascular coagulation was uncommon and the extent of disease was not correlated with hypercoagulability. TEG(TG) showed good correlation with fibrinogen (r=0.80) and hyperfibrinogenemia seems to be a main factor of the hypercoagulable state in carcinoma dogs. In conclusion, TEG(TG) is a valid parameter to diagnose hypercoagulability.     

An Inherited Platelet Function Defect in Basset Hounds

An inherited platelet function defect occurring in a family of basset hounds has been described. The trait is transmitted as an autosomal characteristic and appears to be expressed clinically only in the homozygous state. The characteristics of this platelet defect include:1) marked bleeding tendencies and prolonged skin bleeding times in either male or female dogs.2) normal blood coagulation mechanism.3) adequate numbers of circulating platelets which appear morphologically normal by light microscopy.4) normal whole blood clot retraction.5) deficient in vivo platelet consumption and in vitro platelet retention in glass bead columns.6) defective ADP-induced platelet aggregation in homozygotes, apparently normal ADP response in heterozygotes, and defective collagen-induced platelet aggregation in both.     

The influence of inflammation and hematocrit on clot strength in canine thromboelastographic hypercoagulability

Objective

To investigate parameters causing canine thromboelastographic hypercoagulability and to investigate whether thromboelastography (TEG) with Cytochalasin D (Cyt D) added is related to parameters of platelet activity.

Design

Prospective observational study on hemostatic and inflammatory parameters. Data were collected between November 2012 and July 2013.

Setting

University teaching hospital.

Animals

Twenty‐eight dogs suffering from diseases predisposing to thrombosis and 19 clinically healthy dogs. Diseased dogs were enrolled if they fulfilled inclusion criteria regarding age, size, informed client consent, and obtained a diagnosis of a disease that has been associated with thrombosis or hypercoagulability.

Interventions

None.

Measurements and Main Results

Parameters of coagulation and anticoagulation, fibrinolysis, and antifibrinolysis, platelet activity, inflammation, platelet count, and hematocrit were measured using CBC, TEG, platelet aggregation on multiplate, platelet activity on flow cytometry, and hemostatic and inflammatory markers on plasma and serum analyses. ANOVA and multilinear regression analyses indicated that especially hematocrit and the inflammatory parameters C‐reactive protein and interleukin‐8 showed best association with overall clot strength in diseased dogs with hypercoagulable TEG tracings. Ratios presumed to reflect platelet contribution to the TEG tracing obtained in TEG analyses with Cyt D were related especially with hematocrit and P‐selectin expression of platelets measured after γ‐Thrombin activation on flow cytometry.

Conclusion

Overall clot strength in TEG analyses of the hypercoagulable dogs included in the present study appears to be primarily associated with inflammation as well as hematocrit. Furthermore, the ratio between standard TEG analyses and TEG analyses with Cyt D may reflect some degree of platelet activity.     

Effects of the glycoprotein IIb/IIIa antagonist abciximab on thrombus formation and platelet function in cats with arterial injury

An established model of arterial injury was used to evaluate the ability of the glycoprotein (GP) IIb/IIIa antagonist abciximab to inhibit platelet function and deter thrombus formation in cats. The study was a blinded evaluation, with control cats receiving aspirin and placebo and treatment cats receiving aspirin plus abciximab. The group treated with aspirin plus abciximab had significantly (P<.05) less thrombus formation based on a smaller number and frequency of cyclic flow reductions and reduced luminal thrombus area than cats treated with aspirin plus placebo. Abciximab administered in addition to aspirin also resulted in significant (P<.05) inhibition of platelet function based on mucosal bleeding time and change in bleeding time from baseline.     

Heterozygosity for P2Y12 receptor gene mutation associated with postoperative hemorrhage in a Greater Swiss Mountain dog

A 3‐year‐old, female Greater Swiss Mountain dog developed a hemoperitoneum following an exploratory laparotomy and ovariohysterectomy. Platelet count, PT, APTT, and plasma von Willebrand factor antigen concentration were within RIs. A buccal mucosal bleeding time (BMBT) was prolonged. Given the probability of a hereditary thrombopathia, the dog was administered desmopressin, fresh platelet transfusions, and aminocaproic acid to control hemorrhage. Subsequently, DNA testing for the P2Y12 receptor gene mutation identified the dog as being a heterozygote (carrier). Further platelet function testing was performed following complete recovery. Results of a repeat BMBT and a point‐of‐care screening test using the Platelet Function Analyzer‐100 (collagen/adenosine‐diphosphate [ADP] test cartridge) were within RIs. Flow cytometric studies demonstrated a marked reduction in fibrinogen binding to the dog's platelets in response to ADP ‐ adenosine diphosphate activation. Likewise, turbidimetric aggregometry revealed a complete absence of platelet aggregation in response to ADP. However, there were a normal aggregation response to the platelet agonist convulxin and a mild reduction in amplitude in response to γ‐thrombin. This is the first report of a dog heterozygous for the P2Y12 receptor gene mutation exhibiting a bleeding tendency and having evidence of impaired platelet function in vitro in response to ADP activation. Given that the mutant allele for the P2Y12 thrombopathia appears to be widespread in the Greater Swiss Mountain dog breed, veterinarians need to be aware that both homozygotes and heterozygotes for this platelet receptor mutation are at risk of developing life‐threatening bleeding following trauma or surgery.     

Effect of hemolysis on canine kaolin‐activated thromboelastography values and ADVIA 2120 platelet activation indices

Background: The impact of hemolysis on thromboelastography (TEG) and platelet activation indices has not been evaluated. Objective: The aim of this study was to investigate the influence of hemolysis induced mechanically (HM) and hemolysis induced by freezing (HF) on TEG, platelet counts (PLT), and platelet activation indicators. Methods: Blood from 17 dogs was divided into the following samples: controls, HM, and HF. HM was induced by 20 repetitions of expulsion of blood through a 23 g needle. Freezing was at −80°C, followed by warming to 37° and dilution with equal parts room temperature blood at 22°C. TEG variables that were examined included reaction time (R), coagulation time (K), angle (α), maximum amplitude (MA), and clot rigidity (G). Platelet indices were measured with the ADVIA 2120 hematology analyzer. Results: Hematocrit (HCT) (mean±SD) for controls, HM, and HF were 0.41±0.02, 0.39±0.03, and 0.25±0.02 L/L, respectively, consistent with decreases in HCT of 4.8% (HM) and 39.0% (HF). HM resulted in decreased R (2.5±0.9 minutes compared with 5.2±1.9 minutes for controls; P<0.001), and HF resulted in increased K (15.2±8.6 minutes compared with 5.3±4.0 minutes in controls; P<0.01) and decreased α (20±11° compared with 46±17° in controls; P<0.001). MA was decreased more in HF samples (26±2 mm) than in HM (38±8 mm) or control samples (49±9 mm; P<0.0001). The same applied to G values. PLT decreased after HM but not after HF. Hemolysis of both types resulted in decreased mean platelet component (MPC) concentration: control, 19.3±2.0, HM 15.5±3.4, and HF 14.3±0.7 g/dL (P<0.0001). Conclusion: In hemolyzed samples decreased MPC and R suggested activated primary and secondary hemostasis, respectively, but decreased MA and G indicated reduced clot firmness, possibly due to hyporeactive platelets. TEG and platelet activation indices should be interpreted cautiously after hemolysis.     

Influence of platelet count,acetylsalicylic acid,von Willebrand's disease,coagulopathies, and haematocrit on results obtained using a platelet function analyser in dogs

The platelet function analyser PFA-100 aspirates blood in vitro from a sample reservoir in disposable test cartridges through a microscopic aperture cut into a biologically active membrane at the end of a capillary. In different cartridges the membrane is coated with collagen and adenosine diphosphate (ADP) or collagen and epinephrine (adrenaline) inducing a platelet plug and closure of the aperture. The closure time and total volume of blood flow through the capillary until closure of its aperture were measured. The correlation between platelet count in samples of thrombocytopenic dogs and results of the collagen/ADP cartridge (closure time: r(S)=-0.579; total volume: r(S)=-0.549) was closer than between platelet count and capillary bleeding time. No significant correlation was observed between platelet count and the results obtained with the collagen/epinephrine cartridge. In addition, a higher sensitivity was obtained for the collagen/ADP cartridge. Injection of acetylsalicylic acid into healthy dogs significantly increased closure time and total volume of both types of cartridges (P<0.01). Two dogs with von Willebrand's disease had abnormal values. In contrast, coagulopathies did not significantly influence the results of the platelet function analyser (P>0.05). Despite adequate sensitivity of measurements using the collagen/ADP cartridge to assess quantitative and qualitative platelet disorders in dogs, the influence of haematocrit (P<0.0001) will limit the clinical application of the analyser.     

Evaluation of a modified thrombelastography assay initiated with recombinant human tissue factor in clinically healthy horses

Background: Thrombelastography (TEG) is used to evaluate the viscoelastic properties of blood during clotting and provides a global assessment of hemostasis and clot lysis. TEG analysis initiated with recombinant human tissue factor (TF) has not been evaluated in clinically healthy horses. Objectives: The purpose of this study was to determine whether TEG results are affected by the time elapsed between sampling and analysis (storage time) of equine blood samples and to establish a preliminary equine reference interval for a modified TEG assay, using recombinant human TF to initiate coagulation. Methods: Citrated blood samples were obtained from 20 clinically healthy adult horses. Thirteen samples were stored for 30, 60, and 120 minutes at room temperature before TEG analysis. Coagulation was initiated by adding 20 μL of CaCl₂ to 330 μL of blood and 10 μL of diluted recombinant TF for a final dilution of 1:3600. Reaction (R) and clotting (K) times, angle (α), and maximum amplitude (MA) were compared between time points. A preliminary reference interval (minimum–maximum values) was determined using data from all 20 horses after 30 minutes of sample storage. Results: There was a significant effect of storage time on R, K, and α but not MA. Reference intervals were: R, 3.65–6.4 minutes; K, 1.8–5.45 minutes; α, 33.4–66.2°; MA, 41.2–64.1 mm; lysis at 30 minutes post‐MA (LY30), <2.75%; and lysis at 60 minutes post‐MA (LY60), 1.55–9.5%. Conclusions: TEG can be performed on equine citrated blood samples using recombinant human TF to activate clot formation. TEG parameters were significantly affected by storage time, suggesting an incomplete inhibition of coagulation in citrated blood.     

Characterization of the cDNA and genomic DNA sequence encoding for the platelet integrin alpha IIB and beta III in a horse with Glanzmann thrombasthenia

Glanzmann thrombasthenia (GT) is characterized by a defect of platelet aggregation. This autosomal recessive genetic disorder is caused by an abnormality of the platelet glycoprotein receptors alpha IIb or beta III. Recently, we identified a horse with clinical and pathological features of GT. The aim of this study was to describe this case of GT at the molecular level. A point mutation from G to C in exon 2 of ITGA2B causing a substitution of the expected amino acid arginine 72 (Arg(72)) by a proline (Pro(72)) was encountered. This amino acid change may result in abnormal structural conformations that yield an inactive alpha IIb subunit. The genomic DNA analysis showed that this horse was homozygous for the missense mutation.     

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).     

Examination of hemostatic parameters to detect hypercoagulability in dogs with severe protein‐losing nephropathy

Objective – To identify hemostatic abnormalities in dogs with protein‐losing nephropathies (PLN) that represent risk factors for pathologic thrombosis. Design – Cross‐sectional observational study of client‐owned dogs with PLN, nonprotein losing renal failure (RF), and systemic illness (SI) exclusive of primary renal disease. Setting – Urban University Referral Center. Animals – A total of 29 dogs (n=11 PLN, n=7 RF, n=11 SI) were enrolled between January 2001 and July 2002. Samples were also collected from 20 clinically normal dogs to serve as hemostasis assay controls. Interventions – None. Hemostasis Testing – Citrate anticoagulated blood was collected for point‐of‐care testing with a viscoelastic monitor (thromboelastograph [TEG]) and citrate plasma was prepared for coagulation screening tests and specific assay of the following hemostatic proteins: antiplasmin, antithrombin, D‐dimer, Factor VIII, fibrinogen, plasminogen, protein C, and von Willebrand factor. Results – Dogs with PLN and RF demonstrated TEG abnormalities consistent with hypercoagulability (eg, short clotting time, high clot amplitude) and both groups had significantly lower antithrombin than the SI group. The PLN dogs had significantly higher protein C than either the RF or SI group. Hyperfibrinogenemia was a consistent finding among all 3 disease groups, and the coagulation index a measure of hypercoagulability derived from TEG parameters, directly correlated with fibrinogen values of all study dogs. Conclusions – Hemostatic abnormalities consistent with systemic hypercoagulability are common in dogs with RF and PLN, however, no prothrombotic factors unique to PLN were identified in our study. The thrombotic tendency of PLN may therefore involve parameters we did not directly assess such as platelet reactivity, fibrinolysis, perturbations in blood flow, and/or endothelial dysfunction. High protein C is a novel finding in PLN dogs of unknown clinical relevance.