Abstract 132: Comparing Time in Therapeutic Range between Point of Care and Tele-Management Patients

Abstract

Introduction: A strong relationship exists between the Time in Therapeutic Range (TTR), bleeding and thromboembolic events. The TTR percentage can be calculated by the following three methods. The Rosendaal method assumes a linear relationship between two INR values, the Cross Section method uses INR values that are within a specified range and at a specific point in time, and the Fraction of INR Results method measures the number of INRs in a specified range over the total number of INRs. Objectives: Compare the TTR between Point of Care (POC) and Tele-Management (TELE) Non-Valvular Atrial Fibrillation (NVAF) patients calculated by the Rosendaal, Cross Section, and Fraction of INR Results methods. Methods: Data was collected retrospectively during the 2014 calendar year for 100 randomly selected patients ≥ 18 years, received warfarin without interruption, and were monitored by the Penn State Hershey Medical Center Anticoagulation Clinic. INR lab values were obtained 14 days after initiating warfarin therapy and the interval between 2 consecutive INR lab values was ≤ 56 days. All patients in this study had a target INR range of (2.0-3.0). There was a total number of 1,889 INR lab values collected for the POC (n=826) and TELE (n=1,063) cohort groups respectively. The mean TTR value was calculated for each patient. When comparing TTR between the POC and TELE cohorts, the two-sample t-test was used for both the Rosendaal and Fraction of INR Results methods and the Chi-Square test was used for the Cross Section method. Results: Illustrated in Table 1, the mean TTR for the entire study sample (n=100) was (72.4%, 70.0%, and 67.6%) for the Rosendaal, Cross Section, and Fraction of INR Results methods respectively. When comparing between the POC and TELE cohorts, the TTR was 72.8% for the POC cohort and 72.0% for the TELE cohort by the Rosendaal method (p=0.81); the TTR was 64.0% for the POC cohort and 76.0% for the TELE cohort by the Cross Section method (p=0.19); and the TTR was 68.3% for the POC cohort and 67.0% for the TELE cohort by the Fraction of INR Results method (p=0.69). Conclusion: The mean TTR percentage did not provide a consistent pattern among the different TTR calculation methods or between the POC and TELE cohort groups. The differences observed between the POC and TELE cohort groups were not statistically significant (all p > 0.05).