A prospective cohort study to identify clinical diagnostic and prognostic markers of primary immune thrombocytopenia in dogs.

BACKGROUND: Primary immune thrombocytopenia (pITP) in dogs presents a diagnostic challenge, and clinical markers of severity are lacking. OBJECTIVES: Identify clinicopathologic features that differentiate pITP from secondary ITP (sITP) and markers related to bleeding severity, transfusion, and survival of dogs with pITP. ANIMALS: Ninety-eight thrombocytopenic dogs (58 pITP and 40 sITP). METHODS: Client-owned dogs with platelet counts <50 000/µL were enrolled in a prospective, multi-institution cohort study. History and treatment information, through a maximum of 7 days, was recorded on standard data forms. Bleeding severity was scored daily using a bleeding assessment tool (DOGiBAT). At-admission blood samples were collected for CBC, biochemistry, C-reactive protein concentration, and coagulation panels, and to measure platelet surface-associated immunoglobulin G (PSAIg) and expression of platelet membrane proteins and phospholipids. Dogs with evidence of coincident disease were classified as sITP. RESULTS: No definitive pITP diagnostic test was found. However, pITP cases were characterized by lower platelet counts, D dimer concentrations, and platelet membrane protein expression than sITP cases. Differentiation between pITP and sITP was further enhanced using logistic regression modeling combining patient sex, coagulation profile, platelet count, D dimer, and PSAIg. A second model of pITP severity indicated that low hematocrit and high BUN concentration were associated with non-survival. Low hematocrit at admission, but not platelet count or DOGiBAT score, was associated with transfusion. CONCLUSIONS AND CLINICAL IMPORTANCE: Pending validation studies, models constructed from at-admission clinicopathologic findings may improve differentiation of pITP from sITP and identify the most severe pITP cases at the time of presentation.

Rectally obtained fecal samples can be used for fecal occult blood testing in dogs, and fecal immunochemical tests do not detect canine or feline blood.

OBJECTIVE: The first objective was to determine if the sample collection method (naturally voided vs digital rectal examination collection) affected fecal occult blood test (FOBT) results. The second objective was to assess the ability of human fecal hemoglobin immunochemical tests to detect canine and feline blood. ANIMALS: 308 privately owned dogs, healthy and sick. METHODS: Guaiac FOBTs were performed on paired voided and rectally obtained canine fecal samples. The kappa statistic was used to assess agreement between the 2 collection methods, and a multivariate regression model was used to identify factors associated with a positive FOBT. Two fecal immunochemical tests (FITs; Hemosure One Step and OC-Light S) were tested with serially diluted human, canine, and feline blood. RESULTS: Voided and rectally obtained samples showed strong FOB-positivity agreement (k = 0.80), with 92.5% concordance and only 13/308 dogs negative on void but positive on rectal. Multivariate analysis showed dogs with gastrointestinal disease (P = .0008, rectal; P = .0001, void) were more likely and heavier dogs (P = .0037, rectal; P = .0022 void) were less likely to test FOBT positive. Health status, fasting status, NSAID use, and age were associated with FOBT results on univariate, but not multivariate, analysis. FITs did not detect canine or feline blood at any concentration while human blood performed as expected. CLINICAL RELEVANCE: Rectally obtained fecal samples can be reliably used for FOBTs. Human FITs may not be suitable for companion animals, but evaluation of other available tests is needed.

Prophylactic use of a lyophilized platelet product for rhinoscopic diagnosis and treatment of sinonasal aspergillosis in a dog with a P2Y12 platelet receptor mutation.

OBJECTIVE: To describe the periprocedural use of a lyophilized platelet product during rhinoscopic diagnosis and treatment of sinonasal aspergillosis in a Greater Swiss Mountain Dog with a P2Y12 platelet receptor disorder. CASE SUMMARY: After the development of severe epistaxis, a Greater Swiss Mountain Dog was diagnosed with thrombopathia secondary to a P2Y12 receptor gene mutation. Concurrent primary nasal disease was also suspected due to persistent mucopurulent nasal discharge. One month after the initial presentation for epistaxis, the dog was readmitted for workup of nasal disease. Computed tomography of the head showed turbinate lysis and regional lymphadenopathy. Because of concern for a high risk of bleeding in a thrombopathic patient subjected to rhinoscopy and nasal biopsies, a lyophilized platelet product was administered prior to the procedure. Rhinoscopic exam revealed fungal plaques consistent with Aspergillus spp. that were later confirmed on fungal culture to be Aspergillus fumigatus. Rhinoscopic biopsies were performed as well as debridement of the fungal plaques, followed by topical administration of clotrimazole solution. Bleeding was minimal during and after the procedure, and the dog recovered uneventfully. NEW OR UNIQUE INFORMATION PROVIDED: This is the first report of the prophylactic use of lyophilized platelets in a thrombopathic patient undergoing an invasive procedure with potential for significant hemorrhage. Minimal bleeding occurred during the procedure, suggesting that lyophilized platelets could be used for the prevention of bleeding in thrombopathic patients undergoing invasive procedures.

Evaluation of coated platelets, a subset of highly procoagulant platelets, in healthy dogs and dogs with neoplasia.

OBJECTIVE: To determine if dogs with neoplasia produce more coated platelets, a subpopulation of activated platelets generated by dual stimulation with thrombin and convulxin, a glycoprotein VI agonist, than healthy control dogs. ANIMALS: Client-owned dogs diagnosed with lymphoma (n = 19) or solid tumors (14) and healthy control dogs (14). PROCEDURES: Platelets were stimulated ex vivo with thrombin and convulxin. Flow cytometry was used to quantify the percentage of coated platelets based on high levels of surface fibrinogen. To compare the percentage of coated platelets between the three groups, an ANOVA was performed followed by pairwise 95% confidence intervals (CI) adjusted for multiple comparisons using Tukey's method. RESULTS: We observed a greater mean percentage of coated platelets in dogs with solid tumors, compared with healthy control dogs, by 10.9 percentage points (95% CI: -1.0, 22.8), and a mean percentage of coated platelets in dogs with lymphoma that was less than healthy control dogs by 0.3 percentage points (95% CI: -11.4, 10.8). CLINICAL RELEVANCE: This study provides the first data-based evidence that dogs with solid tumors may have a greater mean coated platelet percentage when compared with healthy control dogs, although there is overlap between groups. Further studies are needed investigating coated platelets in specific subsets of neoplasia and investigating additional mechanisms of hypercoagulability in dogs with neoplasia.

Preliminary evaluation of a flow cytometric assay with microsphere controls for the detection of platelet-bound antibodies in canine immune thrombocytopenia.

BACKGROUND: Canine immune thrombocytopenia (ITP) ranges from a mild to severe bleeding disorder, and platelet counts do not reliably predict clinical disease course. The detection of platelet autoantibodies may further define the disease phenotype, but variability in assay configurations and a lack of well-characterized controls limit the diagnostic utility of anti-platelet antibody assays. OBJECTIVES: We aimed to develop control reagents to facilitate the characterization of canine platelet surface-associated immunoglobulin (PSAIg) in flow cytometric assays. METHODS: Silica microspheres were coated with canine IgG and IgM to assess the reactivity of goat and rabbit origin anti-canine immunoglobulin reagents. They were also used as positive controls in the PSAIg assay. Preliminary assay evaluation and determination of sample stability used PRP isolated from seven healthy dogs and 26 dogs newly diagnosed with thrombocytopenia. RESULTS: Blood sample stability was established for up to a 48-hour storage time. The conjugated positive control microspheres demonstrated stable fluorescent labeling over a 2-year observation period. Rabbit and goat origin anti-dog IgM fluorescent antibody labels reacted nonspecifically with canine IgG. Rabbit origin anti-dog IgG antibody demonstrated greater class specificity for canine IgG than a goat origin antibody. Thrombocytopenic dogs had a broad range of membrane-bound immunoglobulin. Median PSAIgG for dogs with primary or secondary ITP (18.4%, 34.1%, respectively) were significantly higher than controls (3.8%, P < .05). CONCLUSIONS: The described assay reagents and procedures provide positive controls and allow consistent thresholding to define a positive test result, suitable for any flow cytometer. A rabbit anti-dog IgG fluorescent label demonstrated specificity for canine IgG and was useful for the detection of PSAIgG in thrombocytopenic dogs.

Platelet number and function in response to a single intravenous dose of vincristine.

BACKGROUND: Vincristine might increase circulating platelet numbers but the functional capacity of these newly released platelets is unknown. OBJECTIVE: To evaluate and compare the functionality of mature and immature (reticulated) platelets after a single intravenous dose of vincristine in dogs. ANIMALS: Ten healthy purpose-bred dogs. METHODS: Dogs prospectively received a single IV injection of 0.02 mg/kg vincristine or 0.9% saline. Before and after treatment on days 3, 5, and 7, platelets (resting and after thrombin stimulation) were assessed by flow cytometric determination of P-selectin (CD62P) expression. Reticulated platelets were distinguished using thiazole orange (TO) staining. RESULTS: Relative to saline, vincristine administration increased platelet count from day 0 to day 7 (225 ± 58 to 273 ± 65 × 103 /µL, vs 299 ± 76.4 to 214 ± 20 × 103 /µL, P = .01) and increased percentage of reticulated platelets from day 0 to day 5 (3.9 ± 1.5% to 6.1 ± 1.6%, P = .02). On all days, reticulated platelets had greater resting expression of CD62P than did mature platelets (49.6 ± 4% vs 10.2 ± 1%, P ≤ .001). Across all days, CD62P expression by reticulated platelets in the vincristine and saline-treated groups was not different when unstimulated (P = .7) or after thrombin stimulation (P = .33). CONCLUSIONS AND CLINICAL IMPORTANCE: Reticulated platelets released in response to vincristine administration function similarly to mature platelets.

Ecological level analysis of primary lung tumors in dogs and cats and environmental radon activity.

BACKGROUND: Epidemiologic studies suggest residential radon exposure might increase the risk of primary lung cancer in people, but these studies are limited by subject mobility. This limitation might be overcome by evaluating the association in pets. HYPOTHESIS: Primary pulmonary neoplasia (PPN) rate is higher in dogs and cats residing in counties with a high radon exposure risk (Environmental Protection Agency [EPA] zone 1) compared to zones 2 (moderate radon exposure risk) and 3 (low radon exposure risk). ANIMALS: Six hundred ninety client-owned dogs and 205 client-owned cats with PPN. METHODS: Retrospective review of medical records at 10 veterinary colleges identified dogs and cats diagnosed with PPN between 2010 and 2015. Each patient's radon exposure was determined by matching the patient's zip code with published county radon exposure risk. County level PPN rates were calculated using the average annual county cat and dog populations. The PPN counts per 100 000 dog/cat years at risk (PPN rates) were compared across radon zones for each species. RESULTS: The PPN rate ratio in counties in high radon zone (1) was approximately 2-fold higher than in counties in lower radon zones for dogs (rate ratio zone 1 to 2, 2.49; 95% confidence interval [CI], 1.56-4.00; rate ratio zone 1 to 3, 2.29; 95% CI, 1.46-3.59) and cats (rate ratio zone 1 to 2, 2.13; 95% CI, 0.95-4.79; zone 1 to 3, 1.81; 95% CI, 0.9-3.61). CONCLUSIONS AND CLINICAL IMPORTANCE: Exposure to household radon might play a role in development of PPN in dogs and cats.

Lyophilized platelets versus cryopreserved platelets for management of bleeding in thrombocytopenic dogs: A multicenter randomized clinical trial.

BACKGROUND: Thrombocytopenia in dogs is common in critical care medicine, but availability of fresh platelet concentrates in veterinary medicine can be limiting. Lyophilized platelets have long shelf-lives and can be easily transported, stored, and administered in various settings. OBJECTIVE: To evaluate the efficacy and safety of a novel trehalose-stabilized canine lyophilized platelet product in thrombocytopenic dogs with clinically-evident bleeding. ANIMALS: Eighty-eight dogs with platelet counts <50 × 103 /µL and a standardized bleeding assessment tool (DOGiBAT) score ≥2. METHODS: Multicenter, randomized, non-blinded, non-inferiority clinical trial comparing dimethyl sulfoxide (DMSO)-stabilized cryopreserved platelet concentrates (CPP) with trehalose-stabilized lyophilized platelets (LP) for control of bleeding in thrombocytopenic dogs. Dogs were randomized to receive 3 × 109 platelets/kg of LP or CPP. Primary outcome measures were change in DOGiBAT score, platelet count, need for additional red cell transfusion and all-cause mortality. RESULTS: Fifty dogs received LP and 38 received CPP. Baseline demographics and clinical characteristics of both groups were comparable. At 1-hour post-transfusion, LP were superior for change in DOGiBAT score, and non-inferior at 24-hours post-transfusion. The LP were non-inferior to CPP for change in platelet count, need for additional red blood cell units, and survival to discharge. The LP were superior for change in hematocrit at 1-hour post-transfusion, and non-inferior at 24-hours. No adverse effects were noted in either group. CONCLUSIONS AND CLINICAL IMPORTANCE: A novel trehalose-stabilized canine LP product appears to be logistically superior and is clinically non-inferior to DMSO-stabilized canine CPP for management of bleeding in thrombocytopenic dogs.

Cell Migration Driven by Self-Generated Integrin Ligand Gradient on Ligand-Labile Surfaces.

Integrin-ligand interaction mediates the adhesion and migration of many metazoan cells. Here, we report a unique mode of cell migration elicited by the lability of integrin ligands. We found that stationary cells spontaneously turn migratory on substrates where integrin ligands are subject to depletion by cellular force. Using TGT, a rupturable molecular linker, we quantitatively tuned the rate of ligand rupture by cellular force and tested platelets (anucleate cells), CHO-K1 cells (nucleated cells), and other cell types on TGT surfaces. These originally stationary cells readily turn motile on the uniform TGT surface, and their motility is correlated with the ligand depletion rate caused by cells. We named this new migration mode ligand-depleting (LD) migration. Through both experiments and simulations, we revealed the biophysical mechanism of LD migration. We found that the cells create and maintain a gradient of ligand surface density underneath the cell body by constantly rupturing local ligands, and the gradient in turn drives and guides cell migration. This is reminiscent of the phenomenon that some liquid droplets or solid beads can spontaneously move on homogeneous surfaces by chemically forming and maintaining a local gradient of surface energy. Here, we showed that cells, as living systems, can harness a similar mechanism to migrate. LD migration is beneficial for cells to maintain adhesion on ligand-labile surfaces, and might also play a role in the migration of cancer cells, immune cells, and platelets that deplete adhesive ligands of the matrix.

Neutrophil extracellular traps in stored canine red blood cell units.

BACKGROUND: Neutrophil extracellular traps (NETs), webs of DNA and citrullinated histones extruded from activated neutrophils cause transfusion-related acute lung injury. Supernatants of stored red blood cell (RBC) units might promote NETosis in neutrophils from the units or from transfusion recipients. HYPOTHESES: (1) NETs form during storage of canine RBC, (2) leukoreduction (LR) before storage of RBC reduces NETosis, and (3) supernatant from stored, nonleukoreduced (NLR) RBC units induces NETosis in healthy canine neutrophils modeling transfusion recipients. ANIMALS: Six healthy purpose-bred research dogs were utilized for blood donation. METHODS: Prospective controlled study. RBC units were collected from each dog, aseptically divided into 2 equal subunits, 1 of which was leukoreduced, and stored for 42 days. Stored units were sampled biweekly for quantification of NET markers citrullinated histone H3 (Western blot) and cell-free DNA (cfDNA) (DNA dye binding). Unit supernatants were applied ex vivo to canine neutrophils and extracellular DNA release representing NETosis was assessed. RESULTS: Markers of NETs increased during RBC storage (cfDNA P < .0001 and citrullinated H3 P = .0002) and were higher in NLR than LR units (day 42 LR cfDNA 0.34 ± 0.82 ng/mL vs day 42 NLR 1361.07 ± 741.00 ng/mL, P < .0001; day 42 LR citrullinated H3 0.19 ± 0.13 AU vs NLR 0.57 ± 0.34 AU, P = .007). Isolated neutrophils did not form NETs when exposed to stored canine RBC supernatant. CONCLUSIONS AND CLINICAL IMPORTANCE: NETosis occurs in stored canine NLR RBC units, and is attenuated by LR before storage. NETs might be mediators of transfusion reactions.

Performance of a Nageotte hemocytometer method and a flow cytometric assay for residual leukocyte quantification in leukoreduced canine packed red blood cells.

OBJECTIVE: To evaluate the performances of a manual Nageotte hemocytometer method and commercial fluorescent bead-based flow cytometric assay for quantifying [rWBC] in leukoreduced canine packed red blood cell (pRBC) units. DESIGN: Prospective study. Five, commercially purchased, double leukoreduced canine pRBC units were spiked with canine leukocytes to create 6 pRBC standards with the following [rWBC]: < 0.1, 0.375, 1.5, 3.0, 6.0, and 24.0 WBC/µL. [rWBC] of each pRBC standard was measured with the Nageotte hemocytometer and flow cytometric techniques. Limit of detection (LoD), linearity, and bias were determined for each method. For each standard, accuracy and precision were calculated; the cumulative accuracy and mean precision for measurements between the LoD and 24.0 WBC/µL were also determined. SETTING: University veterinary blood bank and clinical pathology laboratory. MEASUREMENTS AND MAIN RESULTS: The Nageotte hemocytometer method had an LoD = 1.48 WBC/µL, inadequate linearity (R2  = 0.92), and a significant negative proportional bias (slope best-fit line = 0.52 ± 0.03). Between [rWBC] 1.5-24 WBC/µL, the technique demonstrated poor cumulative accuracy (6.7%) but acceptable mean precision (17.3%). Relative to a 2 rWBC/µL threshold, at 1.5 WBC/µL the method was inaccurate (6.7%) with acceptable precision (16.6%). The flow cytometric assay had an LoD = 1.3 WBC/µL, acceptable linearity (R2  = 0.99), and a mild positive proportional bias (slope best-fit line = 1.11 ± 0.01). The technique had acceptable cumulative accuracy (80%) and mean precision (10.7%) for measuring [rWBC] between 1.5 and 24 WBC/µL. At 1.5 WBC/µL, this method was acceptably accurate (86.7%) and precise (16.0%). CONCLUSIONS: The flow cytometric assay demonstrated acceptable performance for quantification of [rWBC] in leukoreduced canine pRBC units. The Nageotte hemocytometer method should be used cautiously due to poor accuracy and significant negative bias.

Neutrophil-Extracellular Traps, Cell-Free DNA, and Immunothrombosis in Companion Animals: A Review.

Immunothrombosis is a potentially beneficial physiological process that aids innate immunity and host defense against pathogen invasion. However, this process can also be damaging when it occurs to excess or in critical blood vessels. Formation of extracellular traps by leukocytes, particularly neutrophils, is central to our understanding of immunothrombosis. In addition to degranulation and phagocytosis, extracellular traps are the third mechanism by which neutrophils combat potential pathogens. These traps consist of extracellular DNA decorated with bactericidal cellular proteins, including elastase, myeloperoxidase, and cathepsins. Neutrophils can release these structures as part of a controlled cell-death process or via a process termed vital NETosis that enables the cells to extrude DNA but remain viable. There is accumulating evidence that NETosis occurs in companion animals, including dogs, horses, and cats, and that it actively contributes to pathogenesis. Numerous studies have been published detailing various methods for identification and quantification of extracellular trap formation, including cell-free DNA, measurements of histones and proteins such as high-mobility group box-1, and techniques involving microscopy and flow cytometry. Here, we outline the present understanding of these phenomena and the mechanisms of extracellular trap formation. We critically review the data regarding measurement of NETosis in companion animals, summarize the existing literature on NETosis in veterinary species, and speculate on what therapeutic options these insights might present to clinicians in the future.

Inaccurate point-of-care blood glucose measurement in a dog with secondary erythrocytosis.

BACKGROUND: Point-of-care (POC) portable blood glucose meters (PBGMs) are convenient and inexpensive tools for assessing patient blood glucose concentrations. They are often used to quickly diagnose hypoglycemia or collect serial glucose readings in diabetic patients. However, POC meters have been previously identified in human and veterinary literature to be inaccurate when utilized in patients with abnormal HCT. This problem may not be reflected in manufacturer guidelines referenced by practitioners in the POC setting. KEY FINDINGS: A 1.5-year-old dog, previously diagnosed with multiple congenital cardiac malformations, right-to-left cardiac shunting and secondary erythrocytosis, presented to a veterinary emergency center minimally responsive and without detectable pulses. PBGM measurement identified hypoglycemia. Following stabilization of the dog, serial glucose assessments showed discordant results between PBGMs and the reference laboratory biochemistry analyzer. A pathological cause for hypoglycemia was not identified and PBGM readings were determined to be erroneously low due to the dog's abnormally high HCT. SIGNIFICANCE: This case demonstrates the limitations of using PBGMs to assess blood glucose in a dog with secondary erythrocytosis. The report emphasizes the need for judicious use of PBGMs in critically ill patients and that these glucometers may not be reliable in patients with abnormal HCT values.

Immune thrombocytopenia (ITP): Pathophysiology update and diagnostic dilemmas.

Immune thrombocytopenia (ITP) is a common autoimmune bleeding disorder. The understanding of ITP pathogenesis is rapidly evolving. We now recognize ITP as a complex and heterogeneous syndrome that results from a combination of humoral and cell-mediated attacks on platelets peripherally and megakaryocytes in the bone marrow. Autoantibody-mediated ITP also varies in the pathway used to clear platelets, which depends on the platelet glycoprotein being targeted. Moreover, ITP patients present with variable bleeding severities and treatment responses that do not closely correlate with platelet count. A gold standard diagnostic test for ITP is lacking, and biomarkers to assess disease severity are in their infancy. This review provides an update on the immunopathogenesis of ITP and summarizes currently available tests for ITP diagnosis, prediction of disease severity, and treatment responses. Given the heterogeneous pathogenesis and clinical presentation of ITP, we highlight the need for the development of diagnostic and prognostic tests that would allow for the individualized management of a complex disease.

ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs.

Immune-mediated hemolytic anemia (IMHA) causes severe anemia in dogs and is associated with considerable morbidity and mortality. Treatment with various immunosuppressive and antithrombotic drugs has been described anecdotally and in previous studies, but little consensus exists among veterinarians as to the optimal regimen to employ and maintain after diagnosis of the disease. To address this inconsistency and provide evidence-based guidelines for treatment of IMHA in dogs, we identified and extracted data from studies published in the veterinary literature. We developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria, explanation of treatment regimens, and validity of statistical methods. In combination with our clinical experience and comparable guidelines for humans afflicted with autoimmune hemolytic anemia, we used the conclusions of this process to make a set of clinical recommendations regarding treatment of IMHA in dogs, which we refined subsequently by conducting several iterations of Delphi review. Additionally, we considered emerging treatments for IMHA in dogs and highlighted areas deserving of future research. Comments were solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted for publication. The resulting document is intended to provide clinical guidelines for management of IMHA in dogs. These guidelines should be implemented pragmatically, with consideration of animal, owner, and veterinary factors that may vary among cases.

ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats.

Immune-mediated hemolytic anemia (IMHA) is an important cause of morbidity and mortality in dogs. IMHA also occurs in cats, although less commonly. IMHA is considered secondary when it can be attributed to an underlying disease, and as primary (idiopathic) if no cause is found. Eliminating diseases that cause IMHA may attenuate or stop immune-mediated erythrocyte destruction, and adverse consequences of long-term immunosuppressive treatment can be avoided. Infections, cancer, drugs, vaccines, and inflammatory processes may be underlying causes of IMHA. Evidence for these comorbidities has not been systematically evaluated, rendering evidence-based decisions difficult. We identified and extracted data from studies published in the veterinary literature and developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria for IMHA, comorbidities, and causality. Succinct evidence summary statements were written, along with screening recommendations. Statements were refined by conducting 3 iterations of Delphi review with panel and task force members. Commentary was solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted. The resulting document is intended to provide clinical guidelines for diagnosis of, and underlying disease screening for, IMHA in dogs and cats. These should be implemented with consideration of animal, owner, and geographical factors.

Endothelial alterations in a canine model of immune thrombocytopenia.

Bleeding heterogeneity amongst patients with immune thrombocytopenia (ITP) is poorly understood. Platelets play a role in maintaining endothelial integrity, and variable thrombocytopenia-induced endothelial changes may influence bleeding severity. Platelet-derived endothelial stabilizers and markers of endothelial integrity in ITP are largely underexplored. We hypothesized that, in a canine ITP model, thrombocytopenia would lead to alterations in the endothelial ultrastructure and that the Von Willebrand factor (vWF) would serve as a marker of endothelial injury associated with thrombocytopenia. Thrombocytopenia was induced in healthy dogs with an antiplatelet antibody infusion; control dogs received an isotype control antibody. Cutaneous biopsies were obtained prior to thrombocytopenia induction, at platelet nadir, 24 hours after nadir, and on platelet recovery. Cutaneous capillaries were assessed by electron microscopy for vessel thickness, the number of pinocytotic vesicles, the number of large vacuoles, and the number of gaps between cells. Pinocytotic vesicles are thought to represent an endothelial membrane reserve that can be used for repair of damaged endothelial cells. Plasma samples were assessed for vWF. ITP dogs had significantly decreased pinocytotic vesicle numbers compared to control dogs (P = 0.0357) and the increase in plasma vWF from baseline to 24 hours correlated directly with the endothelial large vacuole score (R = 0.99103; P < 0.0001). This direct correlation between plasma vWF and the number of large vacuoles, representing the vesiculo-vacuolar organelle (VVO), a permeability structure, suggests that circulating vWF could serve as a biomarker for endothelial alterations and potentially a predictor of thrombocytopenic bleeding. Overall, our results indicate that endothelial damage occurs in the canine ITP model and variability in the degree of endothelial damage may account for differences in the bleeding phenotype among patients with ITP.

Relative Oral Bioavailability of Two Amoxicillin-Clavulanic Acid Formulations in Healthy Dogs: A Pilot Study.

The use of human generic amoxicillin-clavulanic acid formulations in veterinary medicine is currently lacking supportive evidence. This pilot study was conducted to determine preliminary pharmacokinetic parameters and relative oral bioavailability of a human generic and veterinary proprietary 4:1 amoxicillin-clavulanic acid formulation in healthy dogs to evaluate whether drug exposure was similar and to determine if further comparative investigation is warranted. Each dog received a single oral dose of each formulation containing 500:125 mg of amoxicillin-clavulanic acid at two separate instances with a 2 wk washout period between product administration. Following drug administration, blood was collected at fixed times over 24 hr to measure plasma amoxicillin and clavulanic acid concentrations using liquid chromatography-mass spectrometry. There were no statistically significant differences between pharmacokinetic parameters of either formulation. Clavulanic acid showed greater between-dog variation in drug exposure between formulations compared with amoxicillin and was also observed to be more variable within the veterinary proprietary formulation. The average relative oral bioavailability was 98.2% (23.6% coefficient of variation) for amoxicillin and 152.6% (64.3% coefficient of variation) for clavulanic acid between formulations. This pilot investigation supports the need for further bioequivalence studies regarding these formulations before commenting on product interchangeability.

Development and implementation of a novel immune thrombocytopenia bleeding score for dogs.

BACKGROUND: A method of quantifying clinical bleeding in dogs with immune thrombocytopenia (ITP) is needed because ITP patients have variable bleeding tendencies that inconsistently correlate with platelet count. A scoring system will facilitate patient comparisons and allow stratification based on bleeding severity in clinical trials. HYPOTHESIS/OBJECTIVES: To develop and evaluate a bleeding assessment tool for dogs, and a training course for improving its consistent implementation. ANIMALS: Client-owned dogs (n = 61) with platelet counts <50,000/µL; 34 classified as primary ITP, 17 as secondary ITP, and 10 as non-ITP. METHODS: A novel bleeding assessment tool, DOGiBAT, comprising bleeding grades from 0 (none) to 2 (severe) at 9 anatomic sites, was developed. Clinicians and technicians completed a training course and quiz before scoring thrombocytopenic patients. The training course was assessed by randomizing student volunteers to take the quiz with or without prior training. A logistic regression model assessed the association between training and quiz performance. The correlation of DOGiBAT score with platelet count and outcome measures was assessed in the thrombocytopenic dogs. RESULTS: Clinicians and technicians consistently applied the DOGiBAT, correctly scoring all quiz cases. The odds of trained students answering correctly were higher than those of untrained students (P < .0001). In clinical cases, DOGiBAT score and platelet count were inversely correlated (rs = -0.527, P < .0001), and DOGiBAT directly correlated with transfusion requirements (rs = 0.512, P < .0001) and hospitalization duration (rs = 0.35, P = .006). CONCLUSIONS AND CLINICAL IMPORTANCE: The DOGiBAT and assessment quiz are simple tools to standardize evaluation of bleeding severity. With further validation, the DOGiBAT may provide a clinically relevant metric to characterize ITP severity and monitor response in treatment trials.

Concurrent renal amyloidosis and thymoma resulting in a fatal ventricular thrombus in a dog.

Thymoma-associated nephropathies have been reported in people but not in dogs. In this report, we describe a dog with thymoma and concurrent renal amyloidosis. A 7-year-old castrated male Weimaraner was presented for progressive anorexia, lethargy, and tachypnea. The dog was diagnosed with azotemia, marked proteinuria, and a thymoma that was surgically removed. Postoperatively, the dog developed a large left ventricular thrombus and was euthanized. Necropsy confirmed the presence of a left ventricular thrombus and histopathology revealed renal amyloidosis. We speculate that the renal amyloidosis occurred secondary to the thymoma, with amyloidosis in turn leading to nephrotic syndrome, hypercoagulability, and ventricular thrombosis. This case illustrates the potential for thymoma-associated nephropathies to occur in dogs and that dogs suspected to have thymoma should have a urinalysis and urine protein creatinine ratio performed as part of the pre-surgical database.