Quality of warfarin control in atrial fibrillation patients in South East Queensland, Australia

Abstract

Background Warfarin is widely prescribed to decrease the risk of stroke in atrial fibrillation (AF) patients. Due to patient variability in response, regular monitoring is required, and time in therapeutic range (TTR) used to indicate quality of warfarin control with a TTR>60% is recommended. Recently, an Australian Government review of anticoagulants identified the need to establish current warfarin control and determine the potential place of the newer oral anticoagulants.

Aim To determine warfarin control by a pathology practice in Queensland, Australia and identify factors influencing TTR.

Methods Retrospective data were collected from Sullivan Nicolaides Pathology, a major pathology practice offering a warfarin care programme in Australia. Patients enrolled in their programme as of September 2014 were included in the study. TTR was calculated using INR test results, and test dates using the Rosendaal method with mean patient TTR were used for analysis and comparison. Exclusions were target therapeutic range outside 2.0–3.0, less than two INR tests and programme treatment time of less than 30 days.

Results The eligible 3692 AF patients had 73.6% of INR tests within the therapeutic range. The mean TTR was 81%, with 97% of patients above a TTR of 60%. TTR was not significantly influenced by age, gender or socioeconomic factors.

Conclusions The observed mean TTR of over 80% is superior to the minimum recommended threshold of 60%. The TTR achieved by the Queensland pathology practice demonstrates that dedicated warfarin programmes can produce high-quality warfarin care, ensuring the full benefit of warfarin for Australian patients.