Evaluation of Time in Therapeutic Range on Warfarin Therapy Between Face-to-Face and Telephone Follow-Up in a VA Medical Center

Abstract

Background: Few studies have evaluated percent time in therapeutic range (TTR) for warfarin managed via face-to-face (FF) to telephone (TELE) visits—all finding no difference between groups. Objective: Compare and evaluate TTR for warfarin in patients who received pharmacist-managed care via FF or TELE. Methods: Single-center, retrospective study. Eligible participants were ≥18 years old, on indefinite warfarin therapy, followed by clinical pharmacists via FF or TELE from 2010 to 2012. Primary outcome (TTR) calculated via Rosendaal method. Event data included rates of any bleeding, significant bleeding, deep vein thrombosis, pulmonary embolism, cerebrovascular accident, hospitalizations, and death. Clinics were also compared by location. Results: Two hundred subjects (90 FF and 110 TELE) were included. Mean TTR was 68.17% and 69.57% in FF and TELE groups, respectively. The FF group had statistically significant higher rates of any bleeding (48.9% vs 30.9%). Rates of significant bleeding in FF versus TELE were not significantly different (6.67% vs 2.73%). The majority followed FF with significant bleeding were at a higher bleeding risk than those followed via TELE. There were low rates of venous thromboembolism (1.1% and 1.8%). Conclusions: TTR was ≥65% for most subjects with minimal variability in TTR between clinics. Mean TTR results for each group were greater and above the threshold that has been commonly described in the literature as quality control, suggesting a progression in implementation of telephone-based anticoagulation management.