Medical Program, James J Peters VA Medical Center, Bronx, NY.
Ann Pharmacother. 2013 Sep;47(9):1210-2. doi: 10.1177/1060028013503129.
To report 2 cases in which point-of-care international normalized ratios (POC-INRs) measured using a Hemochron Jr. Signature Elite device (International Technidyne Corporation) were inaccurate in rivaroxaban-treated patients.
Therapy in an 86-year-old man with atrial fibrillation was converted from warfarin to rivaroxaban 15 mg twice daily because of a deep venous thrombotic event despite an INR of 2.4, which was within the therapeutic range. One week later a POC-INR was inadvertently measured, which was 6.3. In light of the POC-INR being markedly elevated, a laboratory test for INR was performed, which gave a result of 2.74. Therapy in a 66-year-old man was converted from war-farin to rivaroxaban 15 mg twice daily because of unstable INRs and a pulmonary embolism despite a therapeutic INR. Seven days after rivaroxaban was started, the patient's POC-INR was 9.2; simultaneously measured laboratory-determined INR was 2.0. For both patients, coagulation tests performed on follow-up visits revealed continued discordance between the POC and laboratory assays.
Rivaroxaban is an oral factor Xa inhibitor with a predictable pharmacokinetic profile, allowing for a fixed-dose regimen without the need for coagulation monitoring. When patients' therapy is switched from rivaroxaban to warfarin, it is recommended that the drugs be given concurrently until the INR is 2.0 or higher, to ensure adequate anticoagulation during this well-recognized vulnerable period for stroke. POC testing is a common method of INR assessment in clinical practice. During ROCKET-AF (Rivaroxaban Once-Daily, Oral, Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation), POC-INRs were measured exclusively with the INRatio device (Hemosense), and values above 4 were seen very rarely (0.25%), which indicates that the values determined in our patients were highly unusual.
Our 2 patients receiving rivaroxaban had POC-INRs elevated beyond what was expected; these measurements were discordant from INRs simultaneously measured via the laboratory. A prospective evaluation assessing the accuracy of other commonly used POC-INR devices in patients receiving rivaroxaban would determine whether our findings extend to other devices. Until that time, laboratory measurement of INR or POC-INR using an INRatio device is recommended when patients' therapy is transitioned from rivaroxaban to warfarin.
报告 2 例使用 Hemochron Jr. Signature Elite 设备（International Technidyne Corporation）测量的即时国际标准化比值（POC-INR）在利伐沙班治疗患者中不准确的情况。
一名 86 岁的心房颤动患者因深静脉血栓形成事件而将华法林转为利伐沙班 15mg，每日两次，尽管 INR 为 2.4，处于治疗范围内。一周后，意外测量了 POC-INR，结果为 6.3。鉴于 POC-INR 明显升高，进行了 INR 实验室检测，结果为 2.74。一名 66 岁的男性因不稳定的 INR 和肺栓塞而将华法林转为利伐沙班 15mg，每日两次治疗，尽管 INR 处于治疗范围内。利伐沙班开始后 7 天，患者的 POC-INR 为 9.2；同时测量的实验室 INR 为 2.0。对于这两名患者，在后续就诊时进行的凝血试验显示 POC 和实验室检测之间持续存在不一致。
利伐沙班是一种口服 Xa 因子抑制剂，具有可预测的药代动力学特征，允许使用固定剂量方案，无需进行凝血监测。当患者的治疗从利伐沙班转换为华法林时，建议同时给予两种药物，直到 INR 达到 2.0 或更高，以确保在此公认的中风脆弱期内充分抗凝。POC 检测是临床实践中评估 INR 的常用方法。在 ROCKET-AF（利伐沙班每日一次，口服，直接 Xa 因子抑制剂与维生素 K 拮抗剂预防心房颤动卒中及栓塞试验）中，仅使用 INRatio 设备（Hemosense）测量 POC-INR，很少见（0.25%）值超过 4，这表明我们患者的测量值非常异常。
我们接受利伐沙班治疗的 2 名患者的 POC-INR 升高超出预期；这些测量值与同时通过实验室测量的 INR 不一致。对接受利伐沙班治疗的患者评估其他常用 POC-INR 设备准确性的前瞻性评估将确定我们的发现是否扩展到其他设备。在此之前，建议当患者的治疗从利伐沙班转换为华法林时，使用 INRatio 设备测量 INR 或 POC-INR 的实验室值。
