If possible, refrain from using the prothrombin time (PT) or activated partial thromboplastin time (APTT) as standalone tests to assess the anticoagulant effect of a NOAC. When possible, laboratories should assess the responsiveness of their locally used PT/APTT reagents to NOAC by testing certified calibrators for PT and APTT to identify the lowest concentration capable of prolonging the clotting time beyond the upper limit of the local normal reference range.
Understanding NOAC effects on available routine coagulation tests may allow qualitative use of routine tests in emergent clinical situations, but these tests do not reliably determine drug concentration.
The effect of NOACs on the screening coagulation assays such as PT, APTT, and TT is directly linked to reagent composition, and clotting time can differ from reagent to reagent, depending on the NOAC’s reagent sensitivity. More accessible tests such as the PT and APTT have important limitations.
