[Evaluation of Portable Coagulation Analyzer in Comparison with Conventional Hospital Laboratory Instrument with Stratification of International Normalized Ratios by Therapeutic Upper Limit].

Point of care devices have been widely applied to outpatients receiving anticoagulation therapy with warfarin for monitoring prothrombin time-international normalized ratio (PT-INR) regularly. However, accuracy in measurement with the device remains undetermined when PT-INR exceeds therapeutic range. We evaluated the performance of a portable CoaguChek XS coagulation analyzer in comparison with a conventional laboratory method according to therapeutic and supra-therapeutic PT-INR values in cardiac outpatients on oral vitamin K antagonists. All participants were classified into 2 groups on the basis of PT-INR 3.0 by the laboratory method; therapeutic group less than or equal to 3.0 (n=48) and supra-therapeutic group above 3.0 (n=8). The correlation coefficients in therapeutic and in supra-therapeutic groups were r=0.82 and r=0.78, respectively (p<0.05). The difference in PT-INR between the laboratory method and the CoaguChek XS was significantly larger in supra-therapeutic group than therapeutic group (1.03±0.73 versus 0.34±0.26, p=0.042). Our study indicates that CoaguChek XS can be useful handheld coagulation analyzer to determine PT-INR rapidly; however, the device may underestimate PT-INR in supra-therapeutic range.