Comparison of four different hematocrit assays and the effect of albumin on their measurements.

Clinical decisions are influenced by hematocrit values. Centrifugation (reference standard), conductivity, optical and impedance methods are often used interchangeably to measure hematocrit. The effects of albumin, which are known to affect conductivity methods, have not been evaluated for limits of agreement (LOA) between hematocrit assays in small animals. Canine venous blood was collected from 74 clinical cases and measured by centrifugation (n = 72), conductivity (n = 73), impedance (n = 24) and optical (n = 50) methods. Bland-Altman analysis determined bias (± SD) and 95% LOA between methods. There was a statistically significant difference between centrifugation hematocrit values and values obtained via conductivity (p < 0.0001), optical (p < 0.0001), and impedance (p = 0.0082) methods. The conductivity method underestimated hematocrit by 2.1 ± 2.9% (95% LOA -3.54 to 7.88), the optical method by 3.1 ± 3.6% (95% LOA -4.0 to 10.2), and the impedance method by 2.3 ± 3.7% (95% LOA -5 to 9.6) when compared to centrifuged hematocrit values. The hematocrit difference between conductivity and centrifugation methods was statistically different for low (4%, 0-5%), within reference limits (3%, -5 to 8%), and high (2%, -2 to 5%) albumin values, respectively (p = 0.02), with post-hoc analysis demonstrating that the difference occurred between the low and high albumin groups. This study confirms that albumin values outside reference limits can affect the conductivity method and that hematocrit values obtained via conductivity, optical and impedance methods underestimate values obtained via centrifugation. Therefore, the hematocrit methods cannot be used interchangeably. The wide limits of agreement also demonstrates that care must be taken when making clinical decisions with different hematocrit methodologies.

Intra- and inter-rater agreement for the detection of band neutrophils and toxic change in horses.

BACKGROUND: The detection of band neutrophils and toxic change via microscopic blood smear review is vitally important, as their presence indicates systemic inflammation. However, in-clinic evaluation of WBC morphology is often limited. OBJECTIVE: We aimed to determine the agreement between expert raters in the detection of bands and toxic change. METHODS: Three board-certified clinical pathologists each evaluated 109 blood smears from horses with acute disease, and 19 control smears from healthy horses. The pathologists determined if bands were present, and if so, the percentage of bands present. They also determined if toxic change was present, and if so, the grade of toxic change. Intra-rater agreement was evaluated using 12 duplicate blood smears. Agreement on the presence of bands between pathologists and an in-clinic hematology analyzer was evaluated. RESULTS: Intra-rater agreement was substantial to almost perfect. Agreement between pathologists for the detection of bands was moderate, but when pathologists agreed bands were present, there was excellent agreement on the percentage of bands and mature neutrophils. Agreement between pathologists for the detection of high-grade, clinically relevant toxic change was fair. When pathologists agreed high-grade toxic change was present, there was fair agreement on Döhle bodies and cytoplasmic basophilia and poor agreement on cytoplasmic vacuolation. Agreement between individual pathologists and the in-clinic hematology analyzer for the indication of bands was fair to moderate. CONCLUSIONS: Consistent identification of bands and toxic change is challenging, even for highly trained personnel. It is, thus,not surprising that in-clinic blood smear evaluation of WBC morphology by non-experts could be inadequate.

Changes in Student Perceptions and Study Strategies Over Time in a Veterinary Clinical Pathology Course Using Case-Based Instruction.

Veterinary students are challenged to develop new, nonlinear ways of thinking as they learn diagnostic reasoning skills. To support this process, we use real-life cases in our clinical pathology course. Changes in student perceptions regarding the use of cases and changes in study strategies over time have not been previously investigated or compared to student grades. Students participated in three voluntary online surveys that included 4-point Likert scale questions and open-ended questions on the helpfulness of cases for learning and study strategies used during the course. We used Friedman tests to detect any differences in perceptions over time; McNemar's test and Wilcoxon signed-rank tests were used to detect any differences in study strategies over time. Fisher's exact tests were used to examine the association between the Likert scale responses and grades in quartiles. Before beginning the course, 29% of students responded that cases were very helpful to their learning, with similar responses for helpfulness in applying course material and grasping important concepts. There was a significant trend of increasing positivity over the duration of the course, with 74% responding that cases were very helpful at the end of the course. The most-reported study strategy was working individually on cases before the midterm (74% of students), and the most helpful study strategy was attending class regularly (88% reported it as very helpful). Study strategies did not change significantly over time. Overall, perceptions and study strategies did not vary significantly with grades.

Multicenter in vitro thromboelastography and thromboelastometry standardization.

OBJECTIVE: To establish and compare the repeatability and reproducibility of activated thromboelastography (TEG) and thromboelastometry (ROTEM) assays. DESIGN: Multicenter in vitro test standardization. SETTING: Veterinary academic centers. ANIMALS: Test samples were obtained from normal, healthy dogs. Sixty identical 5 mL aliquots of canine platelet-rich plasma collected by apheresis, frozen in 6% dimethyl sulfoxide, were tested initially. Sixty identical 6 mL aliquots of canine fresh frozen plasma with admixed cryoprecipitate were subsequently evaluated. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Frozen study samples, quality controls, reagents, and consumables were distributed to participating centers (7 TEG and 3 ROTEM). TEG centers analyzed study samples with kaolin and tissue factor activated assays; ROTEM centers ran proprietary ellagic acid activated and tissue factor activated assays. All machines underwent quality control prior to sample analysis. Within- and between-center coefficients of variation (CVs) were calculated and compared using Mann-Whitney tests and calculation of intraclass correlation coefficients. Within and between centers, individual parameters for both TEG and ROTEM assays were comparable. Both within-center and between-center CVs varied markedly (0.7-120.5% and 1.4-116.5%, respectively) with assay type, instrument, and parameter. CVs for equivalent parameters were not significantly different between the 2 platforms. Intraclass correlation coefficients suggested moderate agreement between centers. In general, individual parameter CVs for platelet-rich plasma samples were lower in TEG centers, while CVs for canine fresh frozen plasma with admixed cryoprecipitate samples were lower in ROTEM centers. CONCLUSIONS: More variation within and between centers was identified than anticipated, but some parameters such as alpha angle were repeatable and reproducible. Sample types for future multicenter standardization efforts will require further optimization and may need to be adapted separately to each platform. Individual centers using viscoelastic tests for evaluation and management of clinical patients should take steps to minimize preanalytical and analytical sources of variation.

Quantifying Novice and Expert Differences in Visual Diagnostic Reasoning in Veterinary Pathology Using Eye-Tracking Technology.

Visual diagnostic reasoning is the cognitive process by which pathologists reach a diagnosis based on visual stimuli (cytologic, histopathologic, or gross imagery). Currently, there is little to no literature examining visual reasoning in veterinary pathology. The objective of the study was to use eye tracking to establish baseline quantitative and qualitative differences between the visual reasoning processes of novice and expert veterinary pathologists viewing cytology specimens. Novice and expert participants were each shown 10 cytology images and asked to formulate a diagnosis while wearing eye-tracking equipment (10 slides) and while concurrently verbalizing their thought processes using the think-aloud protocol (5 slides). Compared to novices, experts demonstrated significantly higher diagnostic accuracy (p <.017), shorter time to diagnosis (p <.017), and a higher percentage of time spent viewing areas of diagnostic interest (p <.017). Experts elicited more key diagnostic features in the think-aloud protocol and had more efficient patterns of eye movement. These findings suggest that experts' fast time to diagnosis, efficient eye-movement patterns, and preference for viewing areas of interest supports system 1 (pattern-recognition) reasoning and script-inductive knowledge structures with system 2 (analytic) reasoning to verify their diagnosis.

The effects of oral administration of Yunnan Baiyao on blood coagulation in beagle dogs as measured by kaolin-activated thromboelastography and buccal mucosal bleeding times.

We examined the effects of oral administration of Yunnan Baiyao (YB) on hemostasis by measuring buccal mucosal bleeding times (BMBTs) and doing citrated kaolin-activated whole-blood thromboelastography (TEG). In a randomized controlled crossover trial 8 beagle dogs were given either placebo or 1000 mg of YB orally every 12 h for 5 consecutive treatments. Blood was drawn 24 h before treatment and 2 and 24 h after the last treatment, and the BMBT was measured in each sample in duplicate. The TEG analysis was done in duplicate 60 ± 5 min after sample collection. There were no adverse effects of treatment and no significant differences between the control and treatment BMBTs or TEG parameters at any time point. Significant differences were found between baseline and 24 h after the last treatment within the treatment group for the TEG parameters LY30 and LY60 and within the control group for the TEG parameters MA, G, LY30, and LY60. Thus, at the dose and frequency of administration in this study YB did not appear to have any clinically significant effects on the measured coagulation parameters. The differences within the treatment group were likely due to analytic error since similar differences were seen in the control group. Further studies with a larger sample, as well as more direct measures of platelet function, are needed.

Nous avons examiné les effets de l'administration orale de Yunnan Baiyao (YB) sur l'hémostase en mesurant le temps de saignement de la muqueuse buccale (TSMB) et en faisant une thromboélastographie (TEG) de sang entier après activation par de la kaoline citratée. Lors d'un essai en croisé randomisé et contrôlé, huit chiens beagle ont reçu soit un placebo ou 1000 mg de YB par voie orale à chaque 12 h pour cinq traitements consécutifs. Du sang a été prélevé 24 h avant le traitement et 2 et 24 h après le dernier traitement, et le TSMB mesuré dans chaque échantillon en duplicata. L'analyse TEG a été faite en duplicata 60 ± 5 min après le prélèvement de l'échantillon. Il n'y eut aucun effet néfaste du traitement et aucune différence significative entre le groupe témoin et le groupe traité pour ce qui est des TSMBs ou des paramètres de la TEG à tous les points d'échantillonnage. Des différences significatives ont été trouvées entre les valeurs de base et 24 h après le dernier traitement à l'intérieur du groupe traité pour les paramètres LY30 et LY60 de la TEG et à l'intérieur du groupe témoin pour les paramètres MA, G, LY30 et LY60 de la TEG. Ainsi, à la dose et à la fréquence d'administration utilisées dans la présente étude, YB ne semble pas avoir d'effet clinique significatif sur les paramètres de coagulation mesurés. Les différences dans le groupe traité sont fort probablement dues à une erreur analytique car des différences similaires ont été notées dans le groupe témoin. Des études supplémentaires avec un échantillonnage plus grand, ainsi que des mesures plus directes de la fonction des plaquettes sont requises.(Traduit par Docteur Serge Messier).

Evaluation of coagulation via thromboelastography in healthy horses administered dexamethasone.

Dexamethasone was administered to healthy horses daily for 7 days. Blood samples were collected at 3 time points from both treatment and non-treatment groups, and analyzed via thromboelastography (TEG). There were no significant differences in TEG parameters between treated and untreated horses, or within treatment groups over time.

Évaluation de la coagulation par une thrombo-élastographie chez des chevaux en santé ayant reçu de de la dexaméthasone. La dexaméthasone a été administrée à des chevaux en santé pendant 7 jours. Des échantillons de sang ont été prélevés à trois moments auprès des groupes de traitement et des groupes sans traitement et ensuite analysés par thrombo-élastographie (TEG). Il n'y avait aucune différence significative dans le temps pour les paramètres TEG entre les chevaux traités et non traités ou à l'intérieur des groupes de traitement.(Traduit par Isabelle Vallières).

Educational interventions to improve cytology visual diagnostic reasoning measured by eye tracking.

The teaching of visual diagnostic reasoning skills, to date, has been conducted in a largely unstructured apprenticeship manner. The purpose of this study was to assess if the introduction of two educational interventions improved the visual diagnostic reasoning skills of novices. These were (1) the active use of key diagnostic features and (2) image repetition. A pre-test and post-test research design was used to compare the two teaching interventions to a traditional teaching group and an expert group using eye tracking as an assessment method. The time to diagnosis and the percentage of time spent viewing an area of diagnostic interest (AOI) were compared using independent t-tests, paired t-tests, and analysis of covariance (ANCOVA). Diagnostic accuracy as a dichotomous variable was compared using Chi-square tables. Students taught in an active-learning manner with image repetition behaved most like experts, with no significant difference from experts for percentage of time spent in the AOIs and a significantly faster time to diagnosis than experts (p<.017). Our results from the educational interventions suggest a greater level of improvement in the eye tracking of students that were taught key diagnostic features in an active-learning forum and were shown multiple case examples.

Comparison of two methods for measurement of equine insulin.

Diagnosis of equine hyperinsulinemia requires an accurate method for quantification of equine insulin concentrations. The objectives of the current study were to compare 2 commercially available techniques for measurement of equine insulin, the radioimmunoassay (RIA) and chemiluminescent immunoassay (CIA). Recovery was poor for both assays, but worse for the CIA. Serial dilution of a high endogenous insulin sample yielded better linearity for the RIA ( r2 = 0.99, P < 0.001) than the CIA ( r2 = 0.92, P = 0.009). Bland-Altman analysis indicated that the CIA was, on average, 91 pmol/l higher than the RIA, with wide limits of agreement (95% limits of agreement: -508 to 691 pmol/l). These findings suggest that results between the assays should not be considered interchangeable.

Systematic evaluation of evidence on veterinary viscoelastic testing part 1: System comparability.

OBJECTIVE: To systematically examine the evidence on system comparability between the thromboelastography and the rotational thromboelastometry viscoelastic point-of-care instruments and to identify knowledge gaps. DESIGN: Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence and quality, and development of consensus on conclusions for application of the concepts to clinical practice. SETTING: Academic and referral veterinary medical centers. RESULTS: Medline via PubMed, CAB abstracts, and Google Scholar were searched. A total of 8 relevant articles were chosen, none were in support of the question, 1 was neutral to the question (level of evidence [LOE] 6, Poor), and 7 were in opposition to the question (LOE 3 Good; LOE 6 Good; LOE 6 Fair; LOE 6 Poor). CONCLUSIONS: Results from the 2 analyzers are not directly comparable and extrapolation of the results from one machine to the other should be avoided. Standardization of the preanalytical variables (eg, blood collection, holding time, and temperature during holding) is strongly recommended. It is recommended that each site create their own "site specific" reference values for each machine and that test samples be compared only to the standardized reference values established at that center. Start-up and consumable costs vary between countries and local comparisons should be performed. Decisions should be made based on the expected use of the machine and if multiple operators will be using it.

Comparison of arterial and venous whole blood clot initiation, formation, and strength by thromboelastography in anesthetized swine.

Thromboelastography (TEG) analysis was used to determine if differences exist between venous and arterial samples in anesthetized swine, using identical sampling techniques for each of the samples. We hypothesized that TEG parameters would not differ between native whole blood venous and arterial samples. Thirty male Landrace swines were included in the study. Both the femoral artery and vein were catheterized using standard cut-down techniques and with identically sized catheters to rule out any catheter size effects on the results. Standard TEG parameters for native whole venous and arterial blood samples (r, K, α, MA, G, and coagulation index) were measured or calculated, and t-test or Mann-Whitney rank-sum test used for comparison when appropriate. Significant differences were detected for r (venous < arterial), K (venous < arterial), α (venous > arterial), and coagulation index (venous > arterial) TEG parameters. No significant differences were measured for MA or G. These differences are important, especially when temporal changes in TEG are utilized to monitor patient stability and fluid therapy protocols using trends in coagulation properties. Taken together, these results suggest that clots are more likely to form at a faster rate in venous samples compared to arterial samples, but the overall clot strength does not differ. Therefore, if TEG analysis is being used to monitor coagulation profiles in a patient, care should be taken to use the same site and technique if results are to be used for comparative purposes.

Comparison of thromboelastography parameters between different catheter lumen diameters in an uncontrolled haemorrhagic shock model in swine.

Sampling technique is a concern for standardization of thromboelastography (TEG), as it contributes towards preanalytical variation in TEG tracings. The objective of this study was to assess the influence of catheter lumen diameter on TEG parameters with kaolin-activated native blood in a swine haemorrhagic shock model, using standardized sampling techniques. We hypothesized that one or more TEG parameters will differ between venous samples collected from catheters with different diameter lumens. Ten male landrace swine were included in the study. Standard cut-down techniques on both femoral veins were performed and catheterized with a 14-gauge (14G) and a 20-gauge (20G) catheter of the same length. Blood withdrawal times were standardized to 3 s and TEG parameters (R, K, α, maximum amplitude, G and coagulation index) were measured or calculated. Significant differences were detected for R (14G < 20G; P = 0.002), K (14G < 20G; P = 0.026), maximum amplitude (14G > 20G; P = 0.02), G (14G > 20G; P = 0.001) and coagulation index (14G > 20G; P < 0.001). No significant differences were measured for α (P = 0.058). Bias values (method A: 20G; method B: 14G) for R, K, α, maximum amplitude, G and coagulation index were 1.00, 0.14, -1.88, -1.56, -1.39 and -1.07, respectively. Using TEG analysis, kaolin-activated native whole blood samples obtained from 14G catheters are hypercoagulable (clotted faster and stronger clot) compared with samples obtained from 20G catheters. Sampling methodology should be standardized and systematic when comparing TEG parameters.

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 kappa 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), alpha-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.