PB0433 - Clinical application of anti-Xa activity assay in rivaroxaban treatment monitoring: A comparison between anti-Xa and HPLC-MS/MS

Background: Rivaroxaban is a safe direct oral anticoagulant which is used in the prevention and treatment of NVAF, thromboembolisms. However, concentration may be affected by liver and so on. Thus, monitoring is necessary for special patients. LC-MS/MS is considered as gold standard but expensive and complex, while APTT and PT are not ideal. In this study, we aimed to establish the correlation of anti-FXa and rivaroxaban drug level for daily use in ordinary labs so as to better guide the rivaroxaban monitoring.

Aims: To analyze the performance of different anti-Xa reagents, and to establish a method for monitoring rivaroxaban treatment.

Methods: This prospective cross-sectional study included 54 patients taking rivaroxaban in the First Hospital of Jilin University from 2021.9-2022.12. Peak, trough concentration and random blood samples were collected. Using automatic coagulation analyzer, APTT and PT were detected using assorted coagulation reagents, and anti-Xa activity was detected using 3 kinds of reagents. Rivaroxaban concentration was detected by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Spearman correlation and linear regression analysis were used for the correlation and predictive value; Bland-Alterman was used to analyze the concordance and bias; Passing-Bablok regression correlation coefficients used for concordance.

Results: Compared with HPLC-MS/MS, correlation coefficients of APTT and PT were 0.364 and 0.363, respectively, which were 0.339 and 0.310 when concentration higher than 78.6; for Zhenyuan, Shandong Ekeda and Japan sysmex, correlation coefficients of rivaroxaban calibrated anti-Xa were 0.92, 0.94 and 0.92, with 95% CIs 0.83-0.96, 0.89-0.97 and 0.84-0.96, respectively. The overall deviations of the 3 reagents were -0.97, 0.61, and -0.28, respectively.The Passing-regression equation slope for rivaroxaban in 3 reagents were 1.06, 1.22 and 0.90, and the Y-intercept were -7.93, 22.18 and 7.80.

Conclusion(s): The anti-Xa test shows high accuracy and reproducibility in rivaroxaban monitoring for clinical application. The coefficients between anti-Xa and rivaroxaban concentration should be considered before use.