title: Comparison of two different ecarin clotting time methods.
abstract: 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.
authors.affiliation: IV. Department of Medicine, University Hospital Mannheim, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany. j-harenberg@t-online.de
authors.forename: Tivadar
authors.initials: T
authors.lastname: Fenyvesi
authors.forename: Job
authors.initials: J
authors.lastname: Harenberg
authors.forename: Christel
authors.initials: C
authors.lastname: Weiss
authors.forename: Ingrid
authors.initials: I
authors.lastname: Jörg
mesh_terms: 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*
chemical_list: D000991:Antithrombins; D001384:Azetidines; D001596:Benzylamines; D006629:Hirudins; D011994:Recombinant Proteins; D014757:Viper Venoms; C109573:melagatran; D010450:Endopeptidases; C020097:ecarin; D005998:Glycine; C083544:lepirudin