Background: In this study, we evaluated the performance of a point-of-care device, the CoaguChek XS Plus system, in the determination of prothrombin time and international normalized ratio (INR) based on ISO17593: 2007 criteria in Taiwanese patients. The underlying clinical and genetic factors were also investigated.
Methods: Fifty patients receiving warfarin therapy were enrolled in this study. The accuracy of the CoaguChek XS Plus system was evaluated with linear regression analysis and bias plot by comparing with the data measured using Sysmex CA-1500. The clinical and genetic factors that may have caused a bias of 0.5 INR were evaluated with Fisher's exact test.
Results: From the 50 patients, 93 INR values were collected by each method. Linear regression analysis indicated a high correlation with r = 0.96, a slope of 1.05, and an intercept of - 0.14. Eight patients showed an INR bias ≥0.5 between the two methods. Only aspartate aminotransferase (AST) >34 U/L (3/8, 37.5% vs. 3/42, 7.1%; p = 0.044) and alanine aminotransferase (ALT) >36 U/L (3/8, 37.5% vs. 3/42, 7.1%; p = 0.044) were significantly different from each other. No differences were observed for hypoalbuminemia, elevated creatinine, anemia, and the polymorphisms of VKORC1 and CYP2C9.
Conclusions: The CoaguChek XS Plus system presented results that were comparable with those obtained using laboratory CA-1500 method. Both methods fell within INR in the range of 2-4.5 defined by ISO17593:2007 and the clinically recognized therapeutic INR range of 2-3.5. Elevated AST and ALT levels might have interfered with the INR results.