An evaluation of 2 prothrombin time/international normalized ratio point-of-care devices in clinical practice: A comparison to the central laboratory international normalized ratio

It is essential that patients receiving anticoagulant treatment with vitamin K antagonists such as warfarin are appropriately monitored using international normalized ratio (INR) results. International normalized ratio results, which are calculated from prothrombin time (PT) determinations, have become the standard unitage for reporting PT results. Typically, blood samples are sent to central laboratories to test plasmas for PT and INR; however, there are many limitations to central laboratory testing. Point-of-care (POC) instruments have been developed to help address many of the problems that exist with centralized laboratory testing-in particular, the efficiency of reporting the result to the patient's health care provider. The purpose of this study was to compare the accuracy of 2 POC devices (HemoSense INRatio System and the ITC Hemochron Jr Signature +) with a standard laboratory plasma coagulation system (Dade Behring BCS with Innovin) in a "real-world" setting. Also, an assessment of clinical accuracy with respect to the appropriate intensity of anticoagulation was determined. A total of 134 patients were tested (76 with HemoSense System and 58 with Hemochron device). We found that both POC instruments showed significant limitations in accuracy compared with the central laboratory method. The POC instruments would have resulted in about 30% misdiagnoses of the patients' therapeutic status. This could potentially result in inappropriate treatment decisions and dose adjustments, especially because there is a relatively narrow therapeutic range for this class of anticoagulants. In conclusion, the results generated by these POC devices are subject to significant limitations.