Abstract TP77: Point Of Care Inr And R-tpa Decision Making In Acute Ischemic Stroke

Abstract

Introduction: IV r-tPA is the standard of care treatment in acute ischemic stroke presenting within 4.5 hours of last known well. Exclusion criteria for administering IV r-tPA include conditions that predispose to bleeding, including an INR of ≥ 1.7 . Point of care (POC) INR testing is significantly faster than laboratory derived INR results and can expedite IV r-tPA administration. However, POC INR testing is less accurate than laboratory-based testing with an acceptable variance range of +/- 0.4, which may lead to improper r-tPA exclusion or inclusion. Objectives: We demonstrate the utility of a protocolized approach to POC INR testing in acute ischemic stroke, in which known or suspected warfarin use requires a lab INR result to determine if r-tPA is contraindicated when POC INR is between 1.3-2.1. This approach prevents IV r-tPA from being inappropriately administered or withheld. Methods: We stratified a subset of real world paired POC and laboratory INR results (n=892) for stroke code patients at our institution from January 1st through July 4 th , 2022 by known or suspected warfarin status and calculated a positive predictive value for POC INR > 1.7. Results: Fifty-four of 892 paired POC and laboratory INR results represented patients with known or suspected warfarin use. Twenty-five (46%) had a POC INR within 1.3-2.1 warranting a lab INR verification prior to safe administration of r-tPA. Thirteen of which had a POC INR < 1.7 but a lab INR of ≥ 1.7. In 5.25% of cases where the POC INR > 1.7 the laboratory INR was < 1.7. The positive predictive value for POC INR >= 1.7 among patients with known or suspected warfarin status is 88.2%. Conclusions: POC INR testing rapidly screens for coagulopathy in IV tPA eligible stroke patients, but due to inherent inaccuracy may inadvertently rule patients in or out for IV r-tPA treatment. Our institution has instituted a policy of requiring laboratory verified INR results when the POC INR is within +/- 0.4 of the laboratory based INR tPA cutoff. In our 892 patient sample, this policy would prevent 13 patients from inadvertently receiving IV tPA due to an inaccurate POC INR. Up to five percent of patients excluded from r-tPA based on POC INR may in-fact be treatment candidates.