# Assessment of Time in Therapeutic Range (TTR) in a Primary Care Warfarin Clinic

## TL;DR

This study evaluates how well patients on warfarin maintain proper blood thinning levels in a primary care clinic, finding room for improvement.

## Contribution

The study provides a retrospective assessment of TTR in a specific primary care setting, revealing suboptimal anticoagulation control.

## Key findings

- The average TTR was 46.7%, indicating poor anticoagulation control in most patients.
- Approximately 29.1% of patients had high bleeding risk due to INR >4.5 at least once.
- Variables like gender, age, and insurance status did not significantly affect TTR.

## Abstract

Background

Anticoagulation is commonly used to prevent thromboembolic events. Warfarin is a cost-effective, widely used anticoagulant that requires close monitoring due to its narrow therapeutic index. Time in therapeutic range (TTR) is a measure of international normalized ratio (INR) control. Using a retrospective approach, we evaluated the TTR of patients using warfarin for anticoagulation in our state-owned urban primary care clinic.

Methods

We conducted a retrospective chart review of adult patients on warfarin therapy followed at an urban Level 1 trauma center’s ambulatory clinic from January to December 2024. Patients with at least two contiguous INR visits over a two-month period were included. Data on warfarin dosing, INR values, anticoagulation visit history, and demographics were extracted from the electronic medical record. The primary outcome was TTR, calculated using the traditional method. Statistical analysis was performed using R-studio.

Results

Overall, 103 patients were analyzed in our clinic. The average TTR was 46.7% for this population. Around 17.5% of patients had a TTR >70%, and 30.1% had a TTR >60%. Approximately 29.1% of patients presented with high bleeding risk (INR >4.5) at least once during the measured time period, with 5.8% of patients requiring ED visits for significant elevations in INR. Variables such as gender, age, and insurance status did not significantly contribute to measured TTR.

Conclusions

The average TTR of our patient population was suboptimal. These findings highlight the need for more targeted quality improvement efforts to enhance anticoagulation management in our primary care clinic. Further evaluation of our current protocol with the help of pharmacists and the enhancement of patient education may be beneficial in achieving this goal.