Determination of Factors Affecting Time in Therapeutic Range in Patients on Warfarin Therapy.

Abstract

Background: The effectiveness and safety of warfarin depend on maintaining an international normalized ratio (INR) within the therapeutic range. Time in Therapeutic Range (TTR) is defined as the percentage of time a patient's INR is within the therapeutic range.

Objective: We sought to determine the factors affecting good TTR in patients on warfarin therapy.

Methods: This was a descriptive cross-sectional study conducted in a single tertiary care center. Good anticoagulation control was defined as TTR ≥65%.

Results: The study population consisted of 518 patients. The mean age was 57.6 ± 12.3 (19-87) and 54.4% of the patients were female. 47.5% patients achieved good anticoagulation control (TTR ≥65%). The mean Medication Adherence Report Scale (MARS) score was significantly higher in patients with good TTR (23.5 ± 1.9 vs. 22.8 ± 2.1, p = .002). Only 40.2% of the patients received education on warfarin. In multivariable analyses, the duration of warfarin therapy >10 years (OR: 2.27, 95% CI: 1.34-3.84, p = .002) and MARS score (OR: 1.22, 95% CI: 1.09-1.35, p < .001) were found to be the independent predictors of the good anticoagulation control.

Conclusion: Duration of warfarin therapy >10 years and MARS score were the independent predictors of good anticoagulation control.