Urgent monitoring of direct oral anticoagulants in patients with atrial fibrillation: a tentative approach based on routine laboratory tests

The number of patients diagnosed with atrial fibrillation who will be candidates for antithrombotic therapy with direct oral anticoagulants (i.e., dabigatran, rivaroxaban, apixaban and edoxaban) is exponentially arising worldwide, thus posing substantial economic and organizational challenges for their urgent monitoring. Due to long turnaround time and inherent technical complexity, liquid chromatography techniques are unsuitable for rapid assessment of their concentration. Even the use of surrogate tests such as thrombin clotting time or anti-factor Xa activity carries some economic and technical drawbacks. Based on literature data, we have hence developed an algorithm based on first-line tests for urgent screening of the anticoagulant effect of direct oral anticoagulants, which entails activated partial thromboplastin time (aPTT) for dabigatran and prothrombin time (PT) for rivaroxaban. Although these tests also display a concentration-dependent prolongation in patients taking apixaban and edoxaban, neither of them is sufficiently sensitive for providing accurate estimation of the pharmacodynamic effect, so that the measurement of anti-factor Xa activity remains the most suitable approach in patients taking these drugs. According to literature data, this strategy appears suitable to reliably define the thrombotic or bleeding risk in an urgent setting, contextually saving precious laboratory resources.