Using a low–molecular weight heparin–calibrated anti–factor Xa assay to assess the concentration of apixaban and rivaroxaban

INTRODUCTION Direct oral anticoagulant (DOAC)-inhibiting factor Xa (FXa-DOAC) are being increasingly used as prophylaxis of venous thromboembolism and for prevention of stroke in patients with atrial fibrillation. In contrast to vitamin K antagonists, DOACs do not require monitoring in general. However, it is sometimes of value in the acute setting, for instance when considering a reversal agent in uncontrolled bleeding in patients on DOAC. METHODS We evaluated if a low-molecular weight heparin (LMWH)-calibrated anti-factor Xa assay could be used to estimate FXa-DOAC concentration in the concentration range