Validation of the Coaguchek® XS INR point-of-care analyser to monitor the INR of patients at Windhoek Central Hospital, Namibia

Abstract

Background: The use of point-of-care INR (international normalised ratio) testing is on the rise because of its ability to facilitate quick clinical decisions as it allows for rapid turnaround time of INR results. Ensuring the quality of these tests is crucial when implementing them in new settings. Objective: This study aimed to assess the sensitivity, specificity, and clinical agreement between the CoaguChek® XS INR meter and the Beckman Coulter ACL 7000 automated coagulometer in outpatients undergoing warfarin therapy. Methods: A prospective cohort design was employed for this comparison. The analysis included Spearman’s correlation, a Bland-Altman plot, and a Cohen’s Kappa analysis of paired INR values. Key outcome measures included the percentage sensitivity, specificity, and clinical agreement of the two methods. A p-value < 0.05 was considered statistically significant. Results: The study involved 89 patients, predominantly female (59.4%), with a mean age of 46 years. Deep vein thrombosis was the most common indication for warfarin therapy (51.9%). The mean difference between INR values determined by the two methods was –0.15 (± 0.27, N = 89), and the Spearman rank correlation coefficient was 0.97 (p < 0.001, N = 89). A clinical agreement of 83.8% (p < 0.05) was obtained. The sensitivity was 94.4%, with specificities of 82.5% for subtherapeutic and 100% for supratherapeutic INRs. Conclusion: The CoaguChek® XS INR meter was proven to be a reliable alternative to the Beckman Coulter ACL 7000 automated coagulometer for monitoring INR results and adjusting warfarin therapy in well-trained patients with stable INR values. What this study adds: The CoaguChek® XS INR meter was proven to be a reliable alternative to the Beckman Coulter ACL 7000 automated coagulometer for monitoring INR results.