The quality of sample acquisition by phlebotomy is variable in its very nature. Therefore, this study evaluated the effects of catheter diameter and blood collection technique on platelet function (impedance-based aggregometry) and variables associated with secondary hemostasis (prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration, and activity of factor VIII), physiologic anticoagulation (activities of antithrombin, protein C, and protein S), and fibrinolysis (fibrin D-dimer concentration) in dogs. Healthy beagle dogs (n = 6) were included in the study. Blood was collected using 4 techniques: (1) through 20-gauge and (2) 18-gauge venous catheters immediately postinsertion in both cephalic veins, (3) through a 14-gauge central venous catheter placed using the Seldinger technique (with a guide wire) in a jugular vein < 30 minutes before collection, and (4) through a 13-gauge central venous catheter placed with a catheter-through-the-needle technique < 30 minutes before sample collection.
Equipment/methodology for analysis included an impedance-based whole blood platelet function analyzer, an automated coagulation analyzer, and kaolin-activated thromboelastography (TEG) analysis. An impedance-based aggregometer with a collagen inductor (0.8, 0.4, 0.2, 0.1, and 0.05 mcg/mL) was used to assess platelet function in hirudin-anticoagulated whole blood. Kaolin-activated TEG variables were assessed in citrated whole blood. PT, aPTT, fibrinogen, fibrin D-dimer, factor VIII, antithrombin, protein C, and protein activities were assessed in citrated plasma. The highest median aggregation rates were observed for techniques 2 and 3 at 0.05 mcg of collagen/mL with 4.3 (range, 2.5–6.5) and 3.7 (range, 2.8–8.3) aggregation units/min. These values did not significantly differ from the other techniques. The coagulation variables examined in this study were not significantly influenced by sample collection technique.
Commentary: This suggests that various blood collection techniques can be used to obtain samples for coagulation testing. However, larger sample sizes and longer-term effects should be employed in future studies to determine whether these results are repeatable and generalizable. This is good news for clinicians who practice in a variety of clinical settings using different types of clinical equipment and tools.—Indu Mani, DVM, DSc
Influence of blood collection technique on platelet function and coagulation variables in dogs. Bauer NB, Er E, Moritz A. AM J VET RES 72:64-72, 2011.
