การศึกษาประสิทธิภาพของการรักษาและควบคุมระดับยาวาร์ฟารินโดยใช้ค่า Time in Therapeutic Range (TTR) ในผู้ป่วยโรงพยาบาลชุมชน

Sujitkun Khantayana

Authors

Sujitkun Khantayana Department of Internal Medicine, Tharongchang Hospital, Suratthani

Keywords:

Atrial fibrillation, Anticoagulant, TTR, Warfarin

Abstract

Background: Warfarin remains the primary oral anticoagulant used in hospitals in Thailand. However, maintaining optimal anticoagulation control is challenging. Time in Therapeutic Range (TTR), with a threshold of TTR ≥65%, is a key indicator for assessing the quality of warfarin therapy. Data from community hospital settings remain limited.

Objectives: To evaluate the quality of anticoagulation control using TTR and to identify factors associated with achieving TTR ≥65%, and to determine the incidence of warfarin-related complications, including bleeding and thromboembolic events.

Methods: A single-center retrospective descriptive study was conducted among patients receiving warfarin at Tharongchang Hospital. Data were collected from medical records between January 1, 2023, and March 1, 2025. TTR was calculated using the Rosendaal method. Descriptive statistics were applied. Continuous variables were compared using Welch’s two-sample t-test, while categorical variables were compared using Pearson’s chi-square test or Fisher’s exact test, as appropriate. Statistical significance was set at p < 0.05. Significant factors were further analyzed using multivariable logistic regression.

Results: Of the 183 patients screened, 162 with complete INR data were included for analysis, with a mean age of 65.2 ± 15.6 years; 54.3% were female. The most common indication for warfarin use was atrial fibrillation (67.9%). The mean TTR was 57.7 ± 20.8%, and 31.5% of patients achieved TTR ≥65%. Patients with antiphospholipid syndrome (APS) or venous thromboembolism (VTE) had the highest mean TTR (64.5%), while the atrial fibrillation group had the lowest (54.5%). Patients with a history of ischemic stroke were more likely to achieve TTR ≥65% (p = 0.032), whereas polypharmacy was associated with a lower likelihood of achieving TTR ≥65% (p = 0.016), both remaining significant after adjustment (adjusted OR 2.62 and 0.38, respectively). Minor bleeding, major bleeding, and acute cardioembolic stroke occurred in 8.0%, 1.9%, and 0.6% of patients, respectively.

Conclusion: Warfarin-treated patients at Tharongchang Hospital achieved a mean TTR of 57.7%. Polypharmacy was significantly associated with suboptimal anticoagulation control. Strategies to improve warfarin management are needed to optimize clinical outcomes.

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