Pseudohyperkalemia in horses with rhabdomyolysis reported by an enzymatic chemistry analyzer.

OBJECTIVE: To investigate pseudohyperkalemia occurring in horses experiencing rhabdomyolysis when serum chemistry profiles are run on an VetScan VS2 analyzer (Abaxis). ANIMALS: 18 horses with rhabdomyolysis (creatine kinase [CK] > 1,000 U/L). METHODS: In 3 horses with serum CK activities > 5,800 U/L and persistent serum potassium concentrations of > 8.5 mmol/L (VetScan VS2), potassium concentrations were reevaluated with either i-STAT Alinity Base Station (Abbott), Catalyst (Idexx), or Cobas c501 (Roche) ion-specific analyzers. Paired serum samples from 15 additional horses (median serum CK activity, 7,601 U/L; range, 1,134 to 192,447 U/L) were analyzed on both VetScan VS2 and Cobas c501 machines. Serum potassium concentrations were compared between the VetScan VS2 and ion-specific analyzers by Bland-Altman and Wilcoxon ranked tests and correlated to log10 CK activity via Pearson correlation. RESULTS: Serum potassium concentrations were significantly higher on the VetScan VS2 (6.7 ± 1.6 mmol/L) versus the ion-specific analyzers (4.0 ± 1.1 mmol/L; P < .0001), with high bias shown in Bland-Altman analysis (43.1 ± 27.9). Potassium concentrations positively correlated with log10 CK activity with the VetScan VS2 (R2 = 0.51; P = .003) but not the Cobas (R2 = 0.09; P = .3) analyzer. CLINICAL RELEVANCE: An alternate analyzer to the VetScan VS2 should be used to evaluate serum potassium concentrations in horses with rhabdomyolysis because the VetScan VS2 methodology uses lactate dehydrogenase, which increases in serum with rhabdomyolysis and falsely elevates potassium concentrations.

Methodology-related pseudohyperkalemia associated with marked muscle enzyme leakage in a dog.

BACKGROUND: As hyperkalemia may be life-threatening, it is critical to recognize artifactually increased potassium concentrations. Pseudohyperkalemia may occur in myopathies when using the VetScan2 analyzer (VS2), but the degree of pseudohyperkalemia and relationships relative to creatine kinase activity (CK) are unknown. OBJECTIVES: We aimed to determine what degree of muscle enzyme leakage, as reflected by increased serum CK activity, results in cases with falsely elevated potassium concentrations when measured by the VS2. We also sought to establish if a linear relationship exists between potassium concentrations measured by the VS2 and CK activity. METHODS: Serum samples from dogs with increased CK activity and with CK activity within the reference interval and without clinically relevant biochemical alterations were used to create diluted samples having various CK activities. Potassium concentrations and CK activities were determined on VS2 and Cobas c501 (Cobas) analyzers. Wilcoxon signed rank, Bland-Altman, and Passing-Bablok analyses were used to compare potassium concentrations generated by the VS2 and Cobas analyzers. Least squares regression analysis was performed to evaluate if a linear relationship exists between VS2 potassium concentrations and Cobas CK activities. RESULTS: Potassium concentrations from the VS2 were higher (median and standard deviation (SD) = 5.2 +/- 0.46 mmol/L) than those from the Cobas analyzer (4.4 +/- 0.35 mmol/L; P < 0.000), and a positive mean bias was found (mean difference = 0.774 mmol/L; 95% Confidence Interval (CI) = 0.706-0.842; limits of agreement = 0.21-1.34). Passing-Bablok regression showed a positive proportional bias for potassium concentrations on the VS2 compared with paired Cobas results (Slope = 1.328; 95% CI = 1.100-1.500) but did not reveal systematic bias (Intercept = -0.714; 95% CI = -1.46-0.265). Least squares regression analysis showed a poor non-significant relationship (R2 = 0.19) between potassium measured by the VS2 and CK measured by the Cobas analyzer. CONCLUSIONS: A defined threshold value of CK activity at which potassium concentration begins to falsely increase when measured on the VS2 was not established as data widely varied. A poor non-significant relationship between potassium concentrations and CK activities did not allow prediction of the threshold at which falsely increased potassium concentrations would be expected on the VS2.

Impact on canine neutrophil preservation with the addition of bovine serum albumin to K3 -EDTA whole blood samples.

BACKGROUND: Cellular deterioration occurs with blood sample aging, impacting white blood cell (WBC) identification and differential accuracy. This may be exacerbated in samples from patients experiencing inflammation. Previously, bovine serum albumin (BSA) has been shown to improve cellular preservation of blood and other samples, but the effect on cell preservation in canine blood has not been assessed. OBJECTIVES: We aimed to determine the effects of BSA on neutrophil nuclear area when added to potassium ethylene diamine tetra-acetic acid (K3 -EDTA)-anticoagulated canine blood prior to blood smear preparation. We evaluated the impact of inflammatory leukograms, sample storage temperatures (4° and 20°C), and time on outcomes. MATERIALS AND METHODS: Canine K3 -EDTA-anticoagulated blood samples stored at 4° and 20°C were used from unique patients, 10 with and 10 without inflammatory leukograms. Blood smears were prepared from aliquots with or without the addition of 22% BSA at 0, 4, 8, 24, 48, and 72 h. The nuclear area was measured for 25 randomly selected neutrophils per slide using Fiji software. Mixed-effect linear regression modeling was performed (significance: P < 0.05). RESULTS: Nuclear area increased over time with and without added BSA. Both sample storage temperatures and the presence or absence of an inflammatory leukogram significantly impacted neutrophil nuclear area. Samples with added BSA had slightly higher predicted nuclear areas than those without BSA, but this difference was not statistically significant. CONCLUSIONS: BSA did not significantly impact neutrophil nuclear area and did not improve neutrophil preservation in canine blood samples.

Babesia vulpes in a dog from Prince Edward Island, Canada.

A 12-year-old neutered male American Staffordshire terrier dog was referred to the Atlantic Veterinary College, Prince Edward Island, Canada, for suspected immune-mediated hemolytic anemia. Babesiosis (Babesia vulpes) was confirmed using polymerase chain reaction testing. The dog was successfully treated with a 10-day protocol of atovaquone/proguanil (TEVA Pharmaceutical Industries, Toronto, Ontario), 13.5 mg/kg BW, PO, q8h and azithromycin (Pharmascience, Montreal, Quebec), 10 mg/kg BW, PO, q24h. To the authors' knowledge, this report is the first documented case of babesiosis caused by Babesia vulpes in a dog from Canada.

Babesia vulpes chez un chien de l'Île-du-Prince-Édouard, Canada. Un chien American Staffordshire terrier mâle castré de 12 ans a été référé au Atlantic Veterinary College, Île-du-Prince-Édouard, Canada, pour suspicion d'anémie hémolytique à médiation immunitaire. La babésiose (Babesia vulpes) a été confirmée à l'aide d'un test d'amplification en chaîne par la polymérase. Le chien a été traité avec succès avec un protocole de 10 jours d'atovaquone/proguanil (TEVA Pharmaceutical Industries, Toronto, Ontario), 13,5 mg/kg BW, PO, q8h et azithromycine (Pharmascience, Montréal, Québec), 10 mg/kg BW, PO, q24h. À la connaissance des auteurs, ce rapport est le premier cas documenté de babésiose causée par Babesia vulpes chez un chien du Canada.(Traduit par Dr Serge Messier).

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

Fine-needle aspiration of cutaneous, subcutaneous, and intracavitary masses in dogs and cats using 22- vs 25-gauge needles.

BACKGROUND: Fine-needle aspiration (FNA) is a common procedure as a diagnostic tool in veterinary medicine. However, it is unclear whether the gauge of the needle affects the quality of cytology. OBJECTIVE: This study compared the quality of cytologic samples obtained via FNA using 22- or 25-gauge needles. METHODS: Fine-needle aspiration was performed on 50 masses (cutaneous, subcutaneous, or intracavitary) obtained from client-owned animals. The size of the needle was randomly assigned using either of the following two sequences: 22-25-22 gauge or 25-22-25 gauge. Samples were evaluated by two board-certified clinical pathologists to assess cellularity, blood contamination, amount of cellular debris, degree of cellular trauma, and the overall ability to make a diagnosis for each sample. RESULTS: No significant difference was detected between the 22- and 25-gauge needle samples for cellularity, whereas a significant difference was present for blood contamination, amount of cellular debris, and degree of cellular trauma. The overall ability to make a diagnosis was not significantly affected by the needle gauge. The degree of cellular trauma was significantly increased in intracavitary samples. CONCLUSIONS AND CLINICAL RELEVANCE: Needle gauge is a contributing factor to FNA sample quality. However, it did not affect the overall ability to make a diagnosis. Samples obtained using 25-gauge needles resulted in less blood contamination yet increased cellular trauma compared to 22-gauge needle samples.

Zinc-induced hemolytic anemia in a dog caused by ingestion of a game-playing die.

A 16-month-old spayed female mixed breed dog was presented with a 1-week history of anorexia, lethargy, diarrhea, vomiting, and difficulty rising. Hematologic evaluation indicated a marked macrocytic hypo-chromic, markedly regenerative anemia. A metallic foreign object in the gastrointestinal tract was identified on abdominal radiographs. Serum zinc concentration was markedly increased.

Granulocytic anaplasmosis in a horse from Nova Scotia caused by infection with Anaplasma phagocytophilum.

A 16-year-old Paint stallion was presented with intermittent fever, inappetance, lethargy, icterus, distal limb edema, and submandibular lymphadenopathy. The horse was native to Nova Scotia and had never left that province. Morulae were detected in granulocytes. Ananaplasma phagocytophilum infection was confirmed by serology and polymerase chain reaction (PCR). The horse responded to treatment with oxytetracycline.

Babesia (Theileria) annae in a red fox (Vulpes vulpes) from Prince Edward Island, Canada.

A 4-6-mo-old female red fox (Vulpes vulpes) was presented to the Atlantic Veterinary College (AVC) Teaching Hospital, Prince Edward Island, Canada. On presentation, the fox was weak and had pale mucous membranes. A complete blood count and a serum biochemistry profile were performed. Blood smear examination revealed low numbers of erythrocytes containing centrally to paracentrally located, single, rarely multiple, approximately 1 x 2 microm, oval to round organisms with morphology similar to Babesia microti. Polymerase chain reaction testing and DNA sequencing of the Babesia species 18S rRNA gene were performed on DNA extracted from whole blood. Results were positive for a Babesia microti-like parasite genetically identical to Babesia (Theileria) annae. The fox was euthanized due to poor prognosis for recovery. Necropsy examination revealed multifocal to locally extensive subacute nonsuppurative meningoencephalitis, an eosinophilic broncho-pneumonia, a moderate diffuse vacuolar hepatopathy, and lesions associated with blunt trauma to the left abdominal region. This is the first reported case of a red fox in Canada infected with a piroplasm. It remains uncertain whether the presence of this hemoparasite in this fox was pathogenic or an incidental finding. The potential for competent vectors of Babesia species on Prince Edward Island, the potential for this Babesia microti-like parasite to infect other wild and domestic canids, and the significance of this parasite to the health of infected individuals are yet to be determined.

Effects of in vitro hemodilution of canine blood on platelet function analysis using the PFA-100.

BACKGROUND: The platelet function analyzer (PFA)-100 is a point-of-care instrument previously evaluated in humans and dogs. In both species, artificially prolonged platelet closure time (CT) occurs with anemia. Reliability of the analyzer in dogs becomes a concern when the HCT is between 0.25 and 0.35 L/L. OBJECTIVE: The objective of this study was to further define the level of HCT at which CT is prolonged, using in vitro diluted canine blood. METHODS: Citrated whole blood samples were collected from 22 healthy dogs. Initial HCT was determined and autologous platelet-rich plasma was added to samples to achieve HCTs of 0.33, 0.30, and 0.27 L/L. CT was determined in duplicate on the PFA-100 using collagen/adenosine-5'-diphosphate cartridges. RESULTS: Compared with the initial CT in samples with HCT 0.39-0.54 L/L (CT mean+/-SD=57.8+/-5.75 seconds), significantly prolonged CTs were found in hemodiluted samples with HCT 0.33 L/L (61.1+/-4.64 seconds), 0.30 L/L (64.3+/-6.79 seconds), and 0.27 L/L (70.8+/-7.90 seconds) (P=0.029; repeated measures ANOVA). CONCLUSION: Although statistical differences were found, further studies are needed to determine the clinical significance of the mild prolongation in CT associated with mild anemia. Until then, dogs with HCTs slightly <0.35 L/L should be evaluated cautiously for platelet dysfunction using the PFA-100.

Evaluation of platelet function in dogs with cardiac disease using the PFA-100 platelet function analyzer.

BACKGROUND: Cardiac disease has the potential to alter platelet function in dogs. Evaluation of platelet function using the PFA-100 analyzer in dogs of multiple breeds and with a broad range of cardiac conditions would help clarify the effect of cardiac disease on platelets. OBJECTIVES: The objective of this study was to assess differences in closure time (CT) in dogs with cardiac disease associated with murmurs, when compared with that of healthy dogs. METHODS: Thirty-nine dogs with cardiac murmurs and turbulent blood flow as determined echocardiographically were included in the study. The dogs represented 23 different breeds. Dogs with murmurs were further divided into those with atrioventricular valvular insufficiency (n=23) and subaortic stenosis (n=9). Fifty-eight clinically healthy dogs were used as controls. CTs were determined in duplicate on a PFA-100 analyzer using collagen/ADP cartridges. RESULTS: Compared with CTs in the control group (mean+/-SD, 57.6+/-5.9 seconds; median, 56.5 seconds; reference interval, 48.0-77.0 seconds), dogs with valvular insufficiency (mean+/-SD, 81.9+/-26.3 seconds; median, 78.0 seconds; range, 52.5-187 seconds), subaortic stenosis (71.4+/-16.5 seconds; median, 66.0 seconds; range, 51.5-95.0 seconds), and all dogs with murmurs combined (79.6+/-24.1 seconds; median, 74.0 seconds; range, 48.0-187 seconds) had significantly prolonged CTs (P<.01). CONCLUSIONS: The PFA-100 analyzer is useful in detecting platelet function defects in dogs with cardiac murmurs, most notably those caused by mitral and/or tricuspid valvular insufficiency or subaortic stenosis. The form of turbulent blood flow does not appear to be an important factor in platelet hypofunction in these forms of cardiac disease.