Abstract
AimsAlthough quantitative anti-FXa assays can be used to measure rivaroxaban plasma levels, they are not widely performed or available. We aimed to tentatively determine the cut-off for thromboembolism and bleeding prevention based on the clotting effect of non-rivaroxaban conjugate-activated FX plasma levels in patients with rivaroxaban using a coagulometric method.Methods and resultsRivaroxaban was added in vitro to normal plasma at a range of 0 to 241 μg/L to cover expected peak and trough levels. Rivaroxaban chromogenic (μg/L) and RVV-confirm as a ratio were determined. Patient plasma samples were assayed with the RVV-confirm reagent. The appropriate rivaroxaban plasma concentration to inhibit clotting mechanisms was based on the remaining FXa in plasma, which was expressed as the ratio of patients/normal, R-C. There is a high correlation between R-C in vitro and spiked normal plasma rivaroxaban concentration (R-Square 0.910, linear equation; 0.971 quadratic equation, p < 0.0001 for both) but not with plasma rivaroxaban chromogenic assays. We propose a cut-off R-C value of 1.65 and 4.5 for safety. Based on the proposed therapeutic range, in 158 assays performed in 58 patients, 6.3 % assays were above the level of bleeding tendency at the peak (R-C 5.39 ± 1.01, median 5.13) and 42 % assays were below the prevention cut-off at the trough (R-C 1.31 ± 0.18, median 1.35).ConclusionsRVVconfirm® is fast and sensitive to measure the effect of rivaroxaban. Clinical studies are needed to establish whether this cut-off is useful for identifying patients at increased risk of hemorrhage or those who exhibit a low level of anticoagulation.
Highlights
The well-established benefits of anticoagulant therapy are significantly hampered by the possibility of thromboembolism or major and sometimes fatal bleeding complications
RVVconfirm® is fast and sensitive to measure the effect of rivaroxaban
Clinical studies are needed to establish whether this cut-off is useful for identifying patients at increased risk of hemorrhage or those who exhibit a low level of anticoagulation
Summary
The well-established benefits of anticoagulant therapy are significantly hampered by the possibility of thromboembolism or major and sometimes fatal bleeding complications. These adverse effects can range from simple external skin bruising and bleeding (epistaxis, gastroduodenal bleeding, pulmonary complications) to problems in vital organs, including temporary or permanent impairment of function (intracranial hemorrhage or embolism), and possibly death. Despite their importance, as well as Altman and Gonzalez Thrombosis Journal (2015) 13:26 between 3 and 14.3 % [1]. The anti-Factor Xa method using chromogenic assay and expressed as μg/L measures the drug concentration and not the intensity of the drug’s anticoagulant activity, and a higher or lower than expected DOACs plasma level does not necessarily indicate an increased risk of bleeding or thrombotic complications [4, 5]
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