Point-of-care ecarin clotting time versus activated clotting time in correlation with bivalirudin concentration

Introduction: A thrombin inhibitor management (TIM) point-of-care test based upon the ecarin clotting time (ECT) has been developed. The ECT has been suggested to more accurately reflect the anti-coagulant effect of direct thrombin inhibitors compared with the activated clotting time (ACT). We sought to examine the correlation of the TIM-ECT test with bivalirudin concentration in patients undergoing percutaneous coronary intervention (PCI), and to compare the performance of this test with the current standard (i.e., ACT). Materials and methods: In a multicenter study, blood samples were obtained at six pre-defined time-points in 170 consecutive patients undergoing PCI using bivalirudin. For each sample, the TIM-ECT (citrated and non-citrated), ACT, and bivalirudin concentration was determined. Results: Considering samples from all time-points (n=784), the correlations of TIM-ECT citrated, TIM-ECT non-citrated, and ACT with bivalirudin concentration were 0.96, 0.93, and 0.90, respectively. For samples collected at therapeutic levels of bivalirudin (n=353), the correlations of TIM-ECT citrated, TIM-ECT non-citrated, and ACT with bivalirudin concentration were lower, and showed a greater disparity between methods, with correlation coefficients of 0.75, 0.59, and 0.37, respectively. Prediction models based on the measured bivalirudin concentration were developed for TIM-ECT and ACT, and the coefficients of determination (r²) of actual versus predicted TIM-ECT and ACT were 0.91 and 0.81, respectively. Conclusions: In this PCI population, the TIM-ECT point-of-care test and ACT demonstrated a strong correlation with bivalirudin concentration. The TIM-ECT test had a higher correlation with bivalirudin concentration at therapeutic levels of the drug, and for individual samples appears to more consistently reflect the bivalirudin concentration compared with the ACT.