Evaluation of Time in Therapeutic Range (TTR) in Patients with Non-Valvular Atrial Fibrillation Receiving Treatment with Warfarin in Tehran, Iran: A Cross-Sectional Study

Abstract

Introduction: Anticoagulant control is assessed by Time in Therapeutic Range (TTR). For a given patient, TTR is defined as the duration of time in which the patient's International Normalized Ratio (INR) values were within a desired range.

Aim: To assess TTR in patients receiving treatment with warfarin for non-valvular atrial fibrillation at a referral center for cardiovascular diseases in Tehran, Iran.

Materials and method: Over 6 months, we enrolled eligible patients presenting to Shaheed Rajaie Hospital in Tehran for regular INR testing. Demographic data, medical history, and current medications were determined for all participants. TTR was assessed by the Rosendaal method.

Results: A total of 470 patients (mean age 58.0±14.2 years, 60.2% women) underwent 1450 INR measurements. The mean TTR was calculated as 54.9±11.9%. Of the sample patients, 37.3% were in the good control category (TTR > 70%), 24.6% were in the intermediate category (50% < TTR < 70%), and 38.1% were in the poor control category (TTR < 50%). The number of current medications above four was a significant predictor of poor control (OR = 2.06; 95% CI, 1.87, 2.23). The mean TTR of the studied patients (54.9%) was below the good control range.

Conclusion: The quality of anticoagulant therapy with warfarin in Iranian patients was poorer than that reported in European countries. Based on these results, research considering the causes of poor TTR among Iranian patients is recommended.

Keywords: Anticoagulant; International Normalized Ratio; Iranian patients.