Comparison of two different ecarin clotting time methods.
BACKGROUND
Ecarin Clotting Time (ECT) assay specifically determines the inhibition of meizothrombin by direct thrombin inhibitors (DTI). Blood coagulation factor levels lowered by vitamin K antagonists (VKA) may prolong ECT. Concomitant treatment of VKA with DTI may influence differently the two published ECT methods.


METHODS
Lepirudin (100-3,000 ng/ml), argatroban (300--3,000 ng/ml) and melagatran (30--1000 ng/ml) were added to normal plasma (NP; n=12) samples and to plasma of patients on stable vitamin K antagonist therapy with warfarin (VKAP; n=12). ECT assays were performed according to [5] (method 1) and according to [6] (method 2). Data were subjected to multifactorial variance analysis.


RESULTS
Normal ranges were 35.5+/-2.8 s in NP versus 31.8+/-1.2 s in VKAP with method 1 (p< 0.001) and 44.3+/-3.9 s in NP vs. 51.4+/-8.3 s in VKAP with method 2 (p< 0.004). Besides the inhibitors (p<0.0001), the method used (p<0.0001) and the group (NP vs. VKAP, p=0.003) had an influence on the ECT. Inhibitors (p< 0.02) or method used (p< 0.03) and the group (NP vs. VKAP, p=0.0001) influenced also the ECT ratio.


CONCLUSIONS
Both ECT methods are suitable for monitoring different DTIs over a large linear range with both methods during concomitant treatments with vitamin K antagonists. The ECT ratio improves but not abolishes the differences between the methods. Additive effects of vitamin K antagonists on ECT methods have to be taken into consideration in clinical routine.
Fenyvesi
Tivadar
T
IV. Department of Medicine, University Hospital Mannheim, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany. j-harenberg@t-online.de
Harenberg
Job
J
Weiss
Christel
C
Jörg
Ingrid
I
D000991:Antithrombins / Q000494:pharmacology*; D001384:Azetidines; D001596:Benzylamines; D001777:Blood Coagulation / Q000187:drug effects*; D010450:Endopeptidases / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006629:Hirudins / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D011994:Recombinant Proteins / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology*
D000991:Antithrombins; D001384:Azetidines; D001596:Benzylamines; D006629:Hirudins; D011994:Recombinant Proteins; D014757:Viper Venoms; C109573:melagatran; D010450:Endopeptidases; C020097:ecarin; D005998:Glycine; C083544:lepirudin