The effects of direct oral anticoagulants apixaban and rivaroxaban on haemostasis tests

Abstract

Aim To determine the effects of the new direct oral anticoagulants (DOACs), rivaroxaban and apixaban, on the results routine and specialised haemostasis tests in Australasian laboratories. These direct inhibitors of Factor X have recently become available for VTE prevention and treatment. They usually do not require laboratory monitoring but, due to their mode of action, they interact with standard haemostasis tests. Also, in situations such as bleeding or emergency surgery, testing to determine the degree of anticoagulation may be helpful. Method Sixteen samples of pooled normal plasma were spiked with several levels of apixaban or rivaroxaban, covering the therapeutic range and beyond. Participants were asked to perform a range of haemostasis tests on each sample as per their current practice. Results Results were analysed for each DOAC concentration, reagent and instrument group. Except at low concentrations, DOACS affect the results of most general and specialised haemostasis tests. Thrombin generation tests were affected at all DOAC concentrations. However, APTT and PT were unaffected by therapeutic levels of apixaban. Discussion For correct interpretation of results, laboratories will need to become familiar with the effects of DOACs on haemostasis tests as performed with their reagents and instruments. Our study provides local data which could be used as a guide to assist with appropriate result assessment in the presence of DOACs.