Sustaining Therapeutic Anticoagulation Control: Seventeen-Year Real-World Experience from a Malaysian Tertiary Cardiac Centre

OBJECTIVES

To evaluate long-term trends in time in therapeutic range (TTR) over 17 years in a prescriber--pharmacist collaborative warfarin medication therapy adherence clinic (MTAC) under a tertiary cardiac centre.

MATERIALS AND METHODS

This retrospective observational study analysed annual clinic-level TTR reports of patients managed at the Warfarin Clinic, Sabah Heart Centre, from 2009 to 2025. Annual TTR was calculated using the Rosendaal method. An extended international normalised ratio (INR) target range was applied from 2009 to 2016, and an exact INR target from 2017 to 2025, reflecting evolving guidelines. Patients were managed under standardized MTAC protocols involving pharmacist-led education, dose adjustment guidance, adherence assessment, and collaboration with prescribers.

RESULTS

Approximately 200--400 patients were followed annually. The overall mean TTR across 17 years was 71.7%, improving from 51.2% in 2009. Annual TTR gradually improved and remained stable over time, ranging from 51.2% to 80.6% during the extended INR range period and from 68.9% to 73.0% during the exact INR range period. Patients anticoagulated for atrial fibrillation or valve replacement consistently achieved higher TTR compared with other indications such as left ventricular thrombus.

CONCLUSION

This 17-year experience demonstrates that high-quality, sustainable warfarin control is achievable in real-world practice through a structured prescriber--pharmacist collaborative MTAC model. The improvement and maintenance of TTR highlight the clinical value of standardized protocols, continuous patient education, and multidisciplinary teamwork. These findings support pharmacist-integrated anticoagulation services and provide a benchmark for quality improvement in warfarin MTAC services across clinical settings.