Late Breaking Original Research
Sunday, November 12, 2023
12:45 PM–02:15 PM
Abstract
Introduction: Warfarin’s narrow therapeutic index and interpatient variability present challenges when optimizing therapy. International normalized ratio (INR) values are used to monitor therapy, but are difficult to predict based on warfarin dosing changes. The primary purpose of this study was to evaluate INR trends compared to warfarin dosage changes to evaluate whether degree of warfarin dosage adjustment could help predict future INR changes.
Research Question or Hypothesis: Can percent INR change be predicted based on warfarin dosage changes in new-start warfarin patients once at steady-state?
Study Design: This was a retrospective chart review of patients newly initiated on warfarin in an inpatient setting.
Methods: Included patients were at least 18 years old, admitted to WVU Hospitals, not on warfarin prior to admission, and had baseline and day 7 INRs. Demographic data, daily warfarin doses, and daily INR values were collected through day 11 of hospitalization. Percent change in daily warfarin dose was calculated and compared to INR percent change after patients were at steady-state. For the primary outcome, mean percent change in warfarin dose was compared to mean percent change in INR values 24 and 48 hours later. Descriptive statistics via means and standard deviations were utilized for statistical analysis.
Results: A total of 183 of 433 patients (42%) received at least 6 consecutive days of warfarin therapy after initiation between January 2019-July 2021 and met inclusion criteria. The mean increase in warfarin dose and INR at 24 and 48 hours later was 10.17% ± 56.97%/9.34% ± 19.06%/6.26% ± 19.89% on day 6, 17.39% ± 72.14%/6.26% ± 19.89%/5.13% ± 20.65% on day 7, 25.46% ± 90.80%/5.13% ± 20.65%/7.32% ± 23.55% on day 8, and 15.30% ± 69.28%/7.32% ± 23.55%/4.38% ± 13.93% on day 9, respectively.
Conclusion: Due to large standard deviations, no direct predictive trends could be determined between warfarin dosage change and INR in our study population.
Presenting Author
Leah Dykstra Student PharmacistWest Virginia University
Authors
Jon P. Wietholter Pharm.D, BCPS, FCCP
West Virginia University School of Pharmacy