Category: Professional Posters
Purpose: Point-of-care (POC) devices, such as CoaguChek XS® allow for more convenient monitoring of international normalization ratio (INR) in patients taking warfarin. The objective of this study was to evaluate and compare the POC INR results obtained by CoaguChek XS®, a venipuncture INR (using STAGO®-Neoplastine® Cl Plus 10 reagent), and a corrected INR developed by a previous study. We also wanted to determine a best-fit correction equation based on our outpatient anticoagulation clinic patient population.
Methods: Patients were sent to the local laboratory for a venipuncture INR if the patient had a POC INR result of 4.0 or greater on CoaguChek XS®. A corrected INR result was calculated during the office visit and that value was used to make a clinical decision. The patient was sent to the laboratory for a venipuncture INR following the office visit. Antiphospholipid antibody syndrome and lupus anticoagulant patients were excluded from the study. INR results were plotted, and a line of best fit was determined.
Results: A total of 50 sets of INR results were collected between February 8, 2016 and May 30, 2019. 36 POC INR results were between an INR of 4.0 and 5.9. 14 POC INR results were between 6.0 and 7.9. The equation that was the best fit for all POC INR results was 0.449 x POC + 1.556 = estimated venipuncture INR. The overall root mean square error was 0.6.
Conclusion: When POC INR is between 4.0 and 5.9 on CoaguChek XS®, correction equations are reliable tools to estimate venipuncture INR, decrease time to clinical decisions, and improve patient satisfaction. Other institutions using the same laboratory reagent could use the INR correction equation determined in this study in lieu of sending patients for venipuncture INR results.