Novel oral anticoagulants: efficacy, laboratory measurement, and approaches to emergent reversal.

Warfarin, the most commonly used of the vitamin K antagonists, has been a mainstay of oral anticoagulation for decades. However, its usage is limited by morbidity and mortality secondary to bleeding as well as a cumbersome therapeutic monitoring process. In the past several years, a number of competing novel oral anticoagulants (NOACs) have been developed, each of which aspires to match or exceed warfarin's effectiveness while mitigating bleeding risk and eliminating therapeutic monitoring requirements. At present, 1 oral direct thrombin inhibitor and 2 direct factor Xa inhibitors are approved by the US Food and Drug Administration. Here, we compare the clinical efficacy and safety profiles of these new drugs. In addition, we discuss various laboratory assays that may be useful to measure these drugs in certain clinical circumstances. Finally, we discuss emerging strategies to reverse these agents in an emergency. The purpose of this article is to provide a framework for practicing pathologists to advise clinicians on NOAC laboratory measurement and management of NOAC-associated bleeding.