Abstract 221: Outcomes Associated with Warfarin Time in Therapeutic Range Among Nonvalvular Atrial Fibrillation Patients Treated in an Integrated Healthcare Delivery System in the U.S.

Abstract

Background: The efficacy of warfarin therapy for stroke risk reduction among nonvalvular atrial fibrillation (NVAF) patients is reduced when its time in therapeutic range (TTR) is not optimal. This study assessed differences in healthcare resource utilization and costs among NVAF patients with different warfarin TTRs in an integrated healthcare delivery system (IHDS) setting in the U.S. Methods: Patients with NVAF were identified from an electronic medical record database (1/1/2004-8/31/2013). Patients were required to have ≥6 international normalized prothrombin time ratio (INR) tests to ensure chronic warfarin therapy. The first INR test was defined as the index event with the corresponding date as the index date. The warfarin TTR of NVAF patients was determined by the modified Rosendaal method. NVAF patients were grouped into two cohorts, those with warfarin TTR <60% (Low TTR) and those with warfarin TTR ≥60% (High TTR). Demographics, clinical characteristics, healthcare resource utilization and costs were evaluated during a 12-month follow-up period. Multivariable regressions were used to assess the impact of different levels of warfarin TTRs on healthcare costs. Results: NVAF patients in the high TTR cohort (n=1,595) had an average warfarin TTR of 73%, while patients in the low TTR cohort (n=1,356) had an average warfarin TTR of 45%. Total all-cause healthcare resource utilization was greater among patients in the low TTR cohort vs. the high TTR cohort (number of all-cause healthcare encounters: 70.2 vs. 56.1, p<0.001). The mean number of all-cause inpatient admissions (0.64 vs. 0.33, p<0.001), hospital length-of-stay (3.3 vs. 1.6 days, p<0.001), and ICU length-of-stay (0.21 vs. 0.09, p=0.02) were significantly greater for the low TTR cohort in comparison to the high TTR cohort during the follow-up period. After adjusting for patient characteristics, total healthcare costs for all-cause and stroke-related healthcare costs were $2,398 (p<0.001) and $687 (p=0.02) higher, respectively for patients in the low TTR cohort vs. the high TTR cohort (Table). Conclusions: NVAF patients with low warfarin TTR, in comparison to those with high warfarin TTR, used more healthcare resources resulting in higher healthcare costs.