Several new oral anticoagulants such as rivaroxaban (which targets Factor Xa) and dabigatran etexilate (which targets thrombin) are in advanced stages of clinical development and are already available for clinical use in some countries. Although these agents do not require routine coagulation monitoring, assays to assess the level of anticoagulation may be of assistance in certain circumstances such as in case of overdose, in patients with a hemorrhagic or thromboembolic event during treatment, or to assess compliance. Moreover, the influence of the new oral anticoagulants on routine coagulation tests must be recognized. The prothrombin time is not suitable for rivaroxaban measurement for several reasons, and the routinely used international normalized ratio for monitoring the vitamin K antagonists cannot be applied to rivaroxaban. Development of universal assays is challenging because the new oral anticoagulants have different targets, and even those with the same target have variable effects on routine coagulation assays. Focusing on rivaroxaban, there is emerging evidence that an anti-Factor Xa assay that uses rivaroxaban-containing plasma calibrators may provide the optimal method for determining plasma rivaroxaban concentrations.
From the *Division of Vascular Medicine and Haemostaseology, Department of Internal Medicine, University Hospital Frankfurt, Frankfurt, Germany; †Hôtel-Dieu University Hospital, Paris, France; ‡Biomnis Laboratories R&D, Ivry-sur-Seine, France; §Hemostasis and Thrombosis Center, Duke University Medical Center, Durham, NC; ‖Departments of Medicine and Biochemistry and Biomedical Sciences, McMaster University and Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario, Canada; and ¶Bayer HealthCare Pharmaceuticals Inc, Montville, NJ.
Received for publication April 29, 2010; accepted July 20, 2010.
The authors received editorial support from Yong-Ling Liu with funding from Bayer Schering Pharma AG and Johnson & Johnson Pharmaceutical Research & Development, LLC.
Theodore E. Spiro is an employee of Bayer HealthCare Pharmaceuticals Inc. E. Lindhoff-Last has acted as a consultant and is a member of the national advisory board of Bayer Schering Pharma AG in Germany. M. M. Samama and J. I. Weitz have acted as consultants for Bayer. T. Ortel has no conflict of interest to disclose.
Correspondence: Edelgard Lindhoff-Last, MD, University Hospital Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany (e-mail: Lindhoffemail@example.com).