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Reproducibility, stability, and biological variability of thrombin generation using calibrated automated thrombography in healthy dogs

BACKGROUND
Thrombin plays a central role in hemostasis and thrombosis. Calibrated automated thrombography (CAT), a thrombin generation assay, may be a useful test for hemostatic disorders in dogs.


OBJECTIVES
To describe CAT results in a group of healthy dogs, and assess preanalytical variables and biological variability.


ANIMALS
Forty healthy dogs were enrolled.


METHODS
Lag time (Lag), time to peak (ttpeak), peak thrombin generation (peak), and endogenous thrombin potential (ETP) were measured. Direct jugular venipuncture and winged-needle catheter-assisted saphenous venipuncture were used to collect samples from each dog, and results were compared between methods. Sample stability at -80°C was assessed over 12 months in a subset of samples. Biological variability of CAT was assessed via nested ANOVA using samples obtained weekly from a subset of 9 dogs for 4 consecutive weeks.


RESULTS
Samples for CAT were stable at -80°C over 12 months of storage. Samples collected via winged-needle catheter venipuncture showed poor repeatability compared to direct venipuncture samples; there was also poor agreement between the 2 sampling methods. Intra-individual variability of CAT parameters was below 25%; inter-individual variability ranged from 36.9% to 78.5%.


CONCLUSIONS
Measurement of thrombin generation using CAT appears to be repeatable in healthy dogs, and samples are stable for at least 12 months when stored at -80°C. Direct venipuncture sampling is recommended for CAT. Low indices of individuality suggest that subject-based reference intervals are more suitable when interpreting CAT results.