Measurement of prothrombin time and activated partial thromboplastin time in citrated whole blood samples from clinically ill dogs following storage

POINT-OF-CARE AND STANDARD LABORATORY REFERENCE INTERVALS FOR COAGULATION VALUES IN ASIAN ELEPHANTS (ELEPHAS MAXIMUS): VARIATION BY AGE CLASS, SEX, AND TIME TO CENTRIFUGATION

In Asian elephants (Elephas maximus), elephant endotheliotropic herpesvirus causes significant calf mortality. Coagulation testing may aid veterinarians in early identification and management of hemostatic disorders. This study sought to establish reference intervals for select coagulation and platelet values. Blood was collected from clinically healthy Asian elephants (n = 63) in juvenile (≤15 yr old, n = 9), adult (>15 to ≤50 yr old, n = 41), and geriatric (>50 yr old, n = 13) age classes at seven institutions in Kanchanaburi Province, Thailand. Activated clotting time (ACT) was immediately assessed with a handheld analyzer, whereas remaining blood was stored at 5°C in sodium citrate and potassium EDTA collection tubes and transported to a central laboratory. Coagulation values were assessed on an automated blood coagulation analyzer, and platelet values were assessed on a hematology analyzer. Reference intervals were established for ACT, prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, platelet count, mean platelet volume, platelet distribution width, and plateletcrit according to the American Society for Veterinary Clinical Pathology guidelines. No significant differences were observed for any value when comparing sex and time to centrifugation. Plasma fibrinogen (P = 0.002) and platelets (P = 0.003) varied significantly by age class, with adults displaying the highest fibrinogen concentrations and geriatric individuals displaying the lowest platelet counts. The ACT kaolin cartridges resulted in high success rates (84.3% feasibility) compared with celite cartridges (4.8% feasibility). Further studies are warranted to stratify reference intervals in accordance with age class trends.

Effects of storage time and temperature on thromboelastographic analysis in dogs and horses

BACKGROUND

The accessibility of thromboelastography (TEG) to general practitioners is limited by short sample storage times (30 minutes) and storage temperatures (20-23°C).

OBJECTIVES

We aimed to evaluate the stability of canine and equine citrated blood samples when stored for extended periods of time, both at room temperature (RT) (20-23°C) and refrigerator temperature (FT) (2-7.5°C).

METHODS

Citrated whole blood samples from healthy dogs and horses (n = 10 for each) were stored for 30 minutes (baseline) at RT before TEG analysis. Baseline values for TEG variables R, K, α, MA, LY30, and LY60 were compared with those from samples stored for 2, 8, and 22.5 h, at RT and FT. Results were compared using an ANOVA (P < .05). Total allowable analytical error (TE_a ) based on biological variation data was used to evaluate stability.

RESULTS

In dogs, statistically significant differences included shorter R, longer K, decreased MA, and increased LY60 at various time points and storage temperatures from 2 h onward. Only samples stored for 2 h at FT showed acceptable stability compared with TE_a . In horses, statistically significant differences included shorter R and K, and decreased α, LY30, and LY60 at various time points and storage temperatures from 2 h onward. Samples were not stable at any time compared with TE_a , regardless of the temperature.

CONCLUSIONS

In this study, canine samples could be stored for up to 2 h at FT without affecting TEG results; equine samples should be stored for 30 minutes at RT.

Retrospective comparison of standard clotting tests and novel clot waveform parameters in dogs using the turbidimetric ACL-TOP CTS 300 coagulation analyzer

Clot waveforms are generated by coagulation analyzers, such as the ACL-TOP, that utilize photo-optical turbidimetric methods to measure prothrombin time (PT) and activated partial thromboplastin time (aPTT), which are standard clotting tests (SCTs). Additional quantitative clot waveform analysis (CWA) parameters include maximum velocity of the PT curve (PT1d), maximum acceleration of the aPTT curve (aPTT2d), and their change in optical density (ODdelta). We explored the potential for CWA to contribute unique information compared to SCTs and quantitative fibrinogen assay (QFA) in dogs with clinical indications for laboratory evaluation of coagulation. We retrospectively evaluated the frequency and agreement between normal, high, and low values of CWA and SCTs for 203 dogs relative to reference intervals (RIs). Most dogs had SCTs within RIs, but most CWA values were high regardless of whether SCT values were within, below, or above the RI. Agreement between SCTs and CWA was slight (kappa <30%). Clinically significant bleeding was noted in 28 of 203 (14%) dogs. SCTs were not different between bleeders and non-bleeders. Median QFA, PT1d, aPTTdelta, and aPTT2d values were statistically significantly higher than RIs in non-bleeders compared to bleeders, whose median values were not below RI. Compared with SCTs, CWA identified differences between the 2 groups. However, wide overlap between the 2 groups limits the use of CWA to clinically discriminate between bleeders and non-bleeders in a heterogeneous population of dogs. Further studies on the diagnostic utility of CWA in coagulopathic dogs are needed.