Comparison of prothrombin time and international normalized ratio values using point-of-care system with a standardized laboratory method in patients on long-term oral anticoagulation – A prospective study

Abstract

Background: In our country, methods of prothrombin time (PT) and international normalized ratio (INR) testing have not been standardized across various centers. Often, we find disparity in INR values from different laboratories, posing a challenge to make an appropriate clinical decision. Objective: The objective of the study was to compare and correlate the PT/INR values using a point-of-care (POC) system with standardized laboratory (SL) testing and to evaluate the efficiency of the POC system in monitoring patients. Methods: We have prospectively compared PT/INR values between a commercially available POC, CoaguChek XS System, Roche, and SL testing in 205 patients and 353 samples from July 2017 to April 2018. Results: The overall strong correlation between POC PT/INR values and simultaneous standard laboratory values was noted. The overall coefficient of correlation among the two groups was 0.919 (P = 0.001) for INR values. In INR range of 2–3.5, the values correlated well with a coefficient of correlation, 0.756 (P = 0.001). In INR range 4. Conclusions: In this comparison study, statistical analysis yielded a good correlation between POC PT/INR values and SL values in therapeutic and subtherapeutic range. POC testing is a good alternative to SL testing. If widely available, POC testing may enable patient self-testing and self-monitoring. In our experience, POC testing had added benefits in emergency settings. However, clinicians and laboratory professionals should be aware of the occasional disagreement between POC INR and standard laboratory INR values.