Detecting clinically relevant rivaroxaban or dabigatran levels by routine coagulation tests or thromboelastography in a cohort of patients with atrial fibrillation

Background: Traditional coagulation tests are included in emergency guidelines for management of patients on direct oral anticoagulants (DOACs) who experience acute bleeding or require surgery. We determined the ability of traditional coagulation tests and fast whole blood thromboelastography (ROTEM (R)) to screen for anticoagulation activity of dabigatran and rivaroxaban as low as 30 ng/mL. Methods: One hundred eighty-four citrated blood samples (75 dabigatran, 109 rivaroxaban) were collected from patients with non-valvular atrial fibrillation (NVAF), to perform screening tests from different manufacturers, (diluted, D) PT, aPTT, TT and ROTEM (R). The activity of DOACs was quantitatively determined by clot detection assays: Hemoclot DTT and DiXal test (Biophen), on CS2100 (Siemens). The clotting time (CT) of INTEM and EXTEM ROTEM (R) (Werfen) were used as test parameters. Results: Dabigatran, >= 30 ng/mL, was accurately detected by five coagulation tests: APTT Actin FSL (93%), PT Neoplastin (93%), APTT Cephascreen, Thromboclotin, and Thrombin (all 100%), but not by PT Innovin (49%). CT-EXTEM (91%) was sufficiently sensitive, but not CT-INTEM (52%). APTT Cephascreen and Thrombin showed good linearity (R-2 = 0.71, R-2 = 0.72). For the other tests linearity was moderate to poor. Rivaroxaban was accurately detected by PT Neoplastin (98%) and less so by APTT Cephascreen (85%). In addition, rivaroxaban was also accurately detected by CT-INTEM (96%). PT Neoplastin showed good linearity (R-2 = 0.81), all other tests had moderate to poor linearity. Conclusion: In patients with NVAF, the ability of routine coagulation tests to detect the presence of significant levels of DOACs is test and reagent dependent. CT-INTEM and CT-EXTEM may be fast whole blood alternatives.