Our May, 2018 Quick Question asks, “How do you measure the oral anti-Xa anticoagulants rivaroxaban, apixaban, edoxaban, and betrixaban?” Here are the answers from our 89 respondents.
- Prothrombin time (PT): 4 (4%)
- Activated partial thromboplastin time (APTT, PTT): 3 (3%)
- Chromogenic anti-Xa assay with specific calibrators: 44 (49%)
- We don’t measure the anti-Xa anticoagulants: 38 (44%)
It is encouraging to learn, despite the US FDA‘s reluctance to approve the use of distributors’ calibrators and controls for rivaroxaban, apixaban, edoxaban, and soon, betrixaban, that a plurality of us are offering this robust method. For those who do not measure, the clamor from our emergency departments is certain to move us to offer the assay soon.
The prothrombin time is the only currently validated assay that estimates some of the anti-Xa DOACs, however the PT is reagent-dependent and cannot provide a low-end value. The PTT may be used to estimate dabigatran, the only oral direct thrombin inhibitor, but its limitations are similar to the limitations of the PT in attempting to measure the anti-Xas.