There are situations where information about the anticoagulant effects of Rivaroxaban could be clinically useful. Methods for measuring Rivaroxaban concentrations are not available at all medical laboratories while the test MRX PT DOAC for measuring the functional effects of Rivaroxaban, in CTR (Clot Time Ratio), can be made available around the clock. The objectives of this study were to investigate CTR in trough and peak samples during Rivaroxaban treatment of atrial fibrillation and to correlate the findings to bleeding episodes. 3 trough- and 3 peak samples from 60 patients (30 on 20 mg daily and 30 on 15 mg daily) were analyzed with PT DOAC. Patients were monitored for 20 months, and bleeding and thrombotic events were documented. Descriptive statistics were used to summarize the data and non-parametric t-test for comparison between groups. ROC curves for the prediction of DOAC plasma levels > 50 ng/mL as determined with LC-MS/MS and anti-FXa methods were computed. There was a significant difference between trough and peak CTR (median CTR 1.33 vs. 3.57, p < 0.001). 28 patients suffered bleeds. Patients on 20 mg Rivaroxaban with bleeds had higher mean peak CTR than patients without bleeds (CTR 4.11 vs. CTR 3.47, p = 0.040). There was no significant difference in mean CTR between patients on 15 mg Rivaroxaban with or without bleeds (CTR 3.81 vs. 3.21, p = 0.803), or when considering all patients (CTR 3.63 vs. 3.56, p = 0.445). Five out of seven patients on Rivaroxaban 20 with mean peak CTR above the dose specific first to third quartile range (Q1-Q3) suffered bleeds, while 7/16 patients with mean peak CTR within, and 1/7 patients with mean peak CTR below the Q1-Q3 suffered bleeds. The area under the ROC curve was > 0.98 at the upper limit of the PT DOAC reference interval and the negative predictive value of PT DOAC for the prediction of DOAC plasma levels > 50 ng/mL was > 0.96. The sample size was too low to draw any firm conclusions but is seems that MRX PT DOAC might be a useful laboratory test in situations where the effect of Rivaroxaban needs evaluation.

中文翻译：

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利伐沙班治疗的房颤患者的凝血时间比 (CTR) 及其与治疗结果的关系

在某些情况下，有关利伐沙班抗凝作用的信息可能在临床上有用。并非所有医学实验室都提供测量利伐沙班浓度的方法，但可以全天候提供用于测量利伐沙班功能影响（CTR（凝血时间比））的测试 MRX PT DOAC。本研究的目的是调查利伐沙班治疗房颤期间谷值和峰值样本的 CTR，并将结果与​​出血事件相关联。使用 PT DOAC 分析了 60 名患者的 3 个谷值和 3 个峰值样本（其中 30 名每天服用 20 mg，30 名每天服用 15 mg）。对患者进行了 20 个月的监测，并记录了出血和血栓事件。使用描述性统计总结数据并使用非参数 t 检验进行组间比较。计算了使用 LC-MS/MS 和抗 FXa 方法测定的 DOAC 血浆水平 > 50 ng/mL 预测的 ROC 曲线。谷值和峰值 CTR 之间存在显着差异（中位 CTR 1.33 与 3.57，p < 0.001）。28名患者出现出血。服用 20 mg 利伐沙班的出血患者的平均峰值 CTR 高于未出血患者（CTR 4.11 与 CTR 3.47，p = 0.040）。服用 15 mg 利伐沙班的有或无出血患者之间的平均 CTR 没有显着差异（CTR 3.81 与 3.21，p = 0.803），或考虑到所有患者（CTR 3.63 与 3.56，p = 0.445）。服用利伐沙班 20 的 7 名患者中，平均峰值 CTR 高于特定剂量第一至第三四分位数范围 (Q1-Q3) 的患者中，有 5 名出现出血，而平均峰值 CTR 在此范围内的患者中有 7/16 名，平均峰值 CTR 低于该范围的患者中有 1/7 名Q1-Q3 出现出血。在 PT DOAC 参考区间上限处，ROC 曲线下面积 > 0.98，PT DOAC 对 DOAC 血浆水平 > 50 ng/mL 的预测的阴性预测值 > 0.96。样本量太小，无法得出任何确切的结论，但在需要评估利伐沙班效果的情况下，MRX PT DOAC 似乎可能是一种有用的实验室测试。