Validation of the international normalized ratio (INR) in a new point‐of‐care system designed for home monitoring of oral anticoagulation therapy

Summary The new CoaguChek XS system is designed for use in patient self testing with a measuring range from 0.8 INR up to 8.0 INR, which has been calibrated against the mean INR of rTF/95 and ERM-AD149. This study was performed to confirm the correct INR results received from two routinely manufactured lots of test strips when compared with the international reference preparations (IRP) rTF/95 and ERM-AD149. At one study site capillary and noncitrated venous whole blood samples from 20 normal donors and 62 anticoagulated patients were applied to two test strip lots of the new system in duplicate. Additionally blood was collected in citrate tubes, processed to plasma, and PT results were obtained using rTF/95 and ERM-AD149 by the manual tilt tube method. Method comparisons of the INR results of the CoaguChek XS system vs. the mean INR of the IRP demonstrated a mean relative bias of −0.02% to −0.4%, mean absolute relative deviations of 6.4–9.6%, and accuracy observing >95% of CoaguChek XS INR within limits of ±14% to ±21.5% to the mean INR of the IRP. The results of the study confirm the successful calibration of two lots of the new CoaguChek XS system, demonstrate the validity of the calibration concept and prove the accuracy of the new system in comparison with the IRP. Clinical decisions in oral anticoagulation therapy may be reliably made upon the INR results of the new system.