A Comparative Study of Portable Monitors (CoaguCheck®XS) for International Normalized Ratio (INR)

Voraporn Poomlek


Objective: To evaluate the accuracy and precision of INR determination of CoaguCheck® XS compared to the standard laboratory method among patients with long-term warfarin therapy.
Methods: 39 patients receiving long-term warfarin were eligible in this study. Parallel INR measurements were performed. Capillary INR (INR_C) measurements were determined with CoaguCheck® XS and venous INR (INR_V) were determined with standard laboratory methods.
Results: We found an excellent correlation coefficient (r2 = 0.968, 95%CI = 0.82 - 0.99) between INR_V and INR_C among 39 patients receiving long-term warfarin. The mean difference between the two methods was 0.16 (p<0.0001). Although these differences were statistically significant, they were not clinically significant. In 97.4% of the INR parallel measurements the differences between the two methods were within 0.5 INR units. The Bland-Altman difference plot showed greater variation with increasing mean INR values. The coefficient of variation of CoaguCheck® XS was 1.07%.
Conclusion: The CoaguCheck® XS was comparable in accuracy to a standard laboratory method. Its precision was good. It might be a suitable alternative to monitor INR values among patients receiving oral anticoagulants by increasing patient compliance with INR monitoring, and facilitating more frequent INR monitoring especially in highly educated patients.



Anticoagulant therapy; CoaguCheck® XS; INR; warfarin

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