In a two centre study (laboratories in Diagnostica Stago and Biomnis) we compared the in vitro effect on thrombin generation (TG) of Dabigatran and Bivalirudin (reversible direct anti-IIa inhibitors) with that of Lepirudin (an irreversible direct anti-IIa inhibitor) spiked into normal pool plasma. The effect of Lepirudin, Bivalirudin and Dabigatran were evaluated in both centres using the CAT (Diagnostica Stago, France) TG method in a concentration ranges up to 5, 20 and 1 μg/mL respectively. Testing was done in triplicate and repeated over 2 days. To reduce assay variability both centres used the same reagents lots and the same normal pool plasma (George King, USA). The range of each drug tested extended well above the therapeutic range concentrations normally found in patient plasma (0.5 to 1.0 μg/mL, 5 to 10 μg/mL and 0.1 to 0.3 μg/mL respectively for Lepirudin, Bivalirudin and Dabigatran). To see the effect of increasing activation forces, TG was performed at 3 different final concentrations of Tissue Factor (TF) - 1, 5 and 20 pM. All reagents were used as recommended by the manufacturer (Thrombinoscope, The Netherlands). A prolongation in the lag time (LT) is observed with all 3 drugs with all 3 concentrations of TF, but this is more marked for Lepirudin and Bivalirudin than it is for Dabigatran. In the therapeutic range Dabigatran (at 5pM TF) shows both an increase in LT and a decrease in peak thrombin and the ETP. At low concentration of Bivalirudin or Lepirudin, there is a paradoxical increase in peak height, which is even more pronounced at low TF concentration. At 1pM TF, this paradoxical peak increase is also observed with Dabigatran.

Results obtained in both laboratories are similar and complement our previous results and those reported elsewhere (1–4). The effect of Lepirudin and Bivalirudin on TG is different from that of Dabigatran. We also note that at lower TF concentration the anticoagulant effect on TG initiation is more intense but the test becomes less reproducible.

Disclosures: Woodhams:Diagnostica Stago: Employment, Full time employee. Carlo:Diagnostica Stago: Employment, Full time employee. Le Flem:Biomnis: Employment, Full time employee of Biomnis. Guinet:Biomnis: Employment, Full time employee of Biomnis. Depasse:Biomnis: Employment, Full Time employee. Samama:Biomnis: Consultancy, Employee of Biomnis, Employment.

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