Phillips Elizabeth M, Buchan Debra A, Newman Nancy, Rajan Arun, Zia Shams
Department of Medicine, State University of New York Upstate Medical University, Syracuse, New York, USA.
Pharmacotherapy. 2005 Oct;25(10):1341-7. doi: 10.1592/phco.2005.25.10.1341.
To compare the international normalized ratio (INR) measured by a point-of-care testing device with that measured by a reference laboratory method for patients receiving either warfarin only or warfarin plus low-molecular-weight heparin (LMWH).
Retrospective study.
Outpatient anticoagulation clinic.
Ninety-one patients receiving warfarin for various indications; 59 of them receiving only warfarin and 32 receiving warfarin plus LMWH.
Capillary blood was obtained for INR determination by a point-of-care device, and venous blood was obtained for INR determination in a standard reference laboratory.
Ninety-one patients had INR pairs run on a point-of-care device and by the laboratory. In both the patients receiving only warfarin and in those receiving warfarin plus LMWH, the mean INR as determined by the point-of-care testing device was statistically significantly higher than the mean INR determined by the laboratory. Although the differences were statistically significant in both groups, the clinical significance of this difference was accentuated in the patients receiving warfarin plus LMWH. The measure of divergence between the point-of-care and laboratory methods was greater in the group receiving warfarin plus LMWH than in the warfarin-only group, with a mean +/- SD percent change between the INR values of 24.19 +/- 27.54% in the warfarin plus LMWH group and 7.21 +/- 17.73% in the warfarin-only group. In assessing the clinical impact of such variability, a greater degree of discordance in dosing adjustment decisions was noted for patients receiving warfarin plus LMWH. In this group, a 25% rate of discordance was noted compared with 8% in the warfarin-only group. Such discrepancy in dosing decisions based on the point-of-care INR would have resulted in discontinuation of LMWH therapy before the patient acquired a true therapeutic INR, with use of the laboratory measurement.
The INR measured with the point-of-care device in patients receiving concurrent LMWH and warfarin therapy may be inaccurate. Patients receiving LMWH in addition to warfarin should have INRs checked by means of the standard reference laboratory method.
比较即时检验设备测定的国际标准化比值（INR）与参考实验室方法测定的INR，研究对象为仅接受华法林治疗或接受华法林加低分子肝素（LMWH）治疗的患者。
回顾性研究。
门诊抗凝诊所。
91例因各种适应证接受华法林治疗的患者；其中59例仅接受华法林治疗，32例接受华法林加LMWH治疗。
采集毛细血管血用即时检验设备测定INR，采集静脉血在标准参考实验室测定INR。
91例患者的INR分别用即时检验设备和实验室方法检测。在仅接受华法林治疗的患者以及接受华法林加LMWH治疗的患者中，即时检验设备测定的平均INR在统计学上显著高于实验室测定的平均INR。虽然两组差异均有统计学意义，但在接受华法林加LMWH治疗的患者中，这种差异的临床意义更为突出。接受华法林加LMWH治疗组即时检验与实验室方法之间的差异程度大于仅接受华法林治疗组，华法林加LMWH组INR值的平均变化百分比为24.19±27.54%，仅接受华法林治疗组为7.21±17.73%。在评估这种变异性的临床影响时，发现接受华法林加LMWH治疗的患者在剂量调整决策上的不一致程度更高。该组的不一致率为25%，而仅接受华法林治疗组为8%。基于即时检验INR的剂量决策差异可能导致在患者通过实验室测量获得真正的治疗性INR之前停用LMWH治疗。
接受LMWH和华法林联合治疗的患者用即时检验设备测定的INR可能不准确。除华法林外还接受LMWH治疗的患者，应采用标准参考实验室方法检查INR。
