Point-of-Care versus Standard Laboratory Method for International Normalized Ratio Testing in a Pharmacy-managed Anticoagulation Clinic

Introduction: Point-of-care (POC) testing devices are increasingly being used in the clinical setting. They are convenient as the tests can be performed in a pharmacy-managed anticoagulation clinic to provide rapid results compared to the standard laboratory method. Therefore, we aimed to determine the agreement between international normalized ratio (INR) levels obtained from a POC device and laboratory instrument. Methods: In a pharmacist-managed anticoagulation clinic, 20 patients receiving oral warfarin therapy had their INR levels measured using a POC device, CoaguChek® XS. During the same visit, another blood sample was collected from each patient for INR measurement and sent to the laboratory in Hospital Raja Perempuan Zainab II, Kelantan. The linear relationship and agreement between INR levels obtained from both methods were analysed using Pearson's correlation and Bland-Altman plot in Statistical Package for Social Sciences (SPSS) version 22.0. Results: The mean (SD) INR levels obtained from POC device and standard laboratory were 2.54 (1.30) and 2.27 (1.01), respectively. There was a significant strong positive correlation between the INR levels obtained from the two methods (r= 0.983, p<0.001). Also, a good agreement was observed between POC device and standard laboratory when INR levels were less than 3.0. Only 1 value at 6.94 fell out of 95% CI. Conclusion: The INR levels obtained from the POC device were comparable to the standard laboratory especially in an outpatient setting. However, in cases whereby the INR levels are in the supratherapeutic range, it is recommended to carry out a laboratory test for result confirmation before any clinical interventions are done