Coagulation Assays in Patients with New Oral Anticoagulants (NOACs): Why? When?


  • Meyer Michel Samama

    Corresponding author
    1. Cochin—Broca—Hôtel Dieu University Hospital, Department of Hematology, Paris, France
    2. Biomnis Laboratory, Ivry-sur-Seine, France
    • Correspondence to: Meyer Michel Samama, Biomnis Laboratory, 78 avenue de Verdun, BP 110, 94208 Ivry-sur-Seine cedex, France.


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  • Conflict of interest: The author declares the following potential conflicts of interest. He is a Consultant for Bayer Schering Pharma AG, Sanofi Aventis, Elli Lilly, and Daiichi Sankyo; a member of advisory board/Steering Committee of B.M.S., Pfizer Laboratory, and Johnson & Johnson. He is an Invited Speaker/Chairperson for Sanofi Aventis, GSK, Bayer Schering Pharma AG, Boehringer-Ingelheim, Rovi Laboratory, and TEM Thromboelastography.


Clinical Development Phases I-III Regulatory, Quality, Manufacturing

Treatment with new oral anticoagulant drugs does not require laboratory monitoring. However, there are some clinical settings where the measurement of the anticoagulant activity can be useful, especially in urgent surgery or invasive procedure. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are prolonged with good correlation with plasma drug concentration. The influence of rivaroxaban on PT is greater than that on aPTT, in contrast to dabigatran. Apixaban responses to PT and aPTT are weak. These tests are not specific and cannot detect low plasma concentrations. For direct Factor-Xa inhibitors, the most appropriate test is a modified anti-Xa chromogenic assay. A specific test unresponsive to heparins and fondaparinux has been developed. For dabigatran measurement, a modified thrombin clotting time, “Hemoclot,” has been well documented. The use of plasma calibrators allows an expression of the results in ng/ml of plasma. Expected peak concentration (2 to 4 h after drug intake) and trough concentration or Cmin—before a repeated administration—have been determined. More clinical work is warranted to determine possible adjustments of the drug according to its plasma concentration. Finally, the potential advantage of a punctual screening during long-term treatment has not been investigated.