COMPARISON OF INTERNATIONAL NORMALIZED RATIO (INR) BETWEEN POINT OF CARE DEVICE COAGUCHEK® XS VERSUS STANDARD LABORATORY INSTRUMENT AMONG PATIENTS RECEIVING WARFARIN THERAPY IN A NORTHEAST STATE OF PENINSULAR MALAYSIA

Abstract

Background: Warfarin is widely used and cost-effective for various indications. However, the narrow therapeutic index of warfarin requires frequent International Normalized Ratio (INR) monitoring. The purpose of this study was to compare the mean differences, to examine the correlation and agreement between the two methods of venipuncture using laboratory assay and by finger prick using Point of Care (POC) device (CoaguChek® XS). Materials and Methods: A cross sectional study was done in warfarin Medication Therapeutic Adherence Clinic (MTAC), Kuala Krai Hospital. Convenient sampling was used to recruit patients from August until December 2016. The INR results from CoaguChek® XS were compared with the results from standard laboratory assay. Descriptive statistics, paired t-test, Pearson's correlation and Bland-Altman plot were used for data analysis. Result: A total of 52 patients with 84 paired samples were collected in this study. The mean INR values obtained from CoaguChek® XS was significantly different from standard laboratory method (p<0.001). However, there was a strong positive correlation between these two methods (r=0.941, p<0.001). Besides, Bland-Altman plot demonstrated a good agreement between both methods especially when INR values less than 3.5. Conclusion: Despite the mean differences of INR values between these two methods was statistically significant, but it was clinically not significant (mean difference = 0.32). There was a strong correlation and good agreement between INR values obtained from these two methods. These findings may help clinicians in improving the quality of INR monitoring for patients on warfarin therapy. Keywords: Point of Care device, standard laboratory method, INR, warfarin.