Objective: To determine the proportion of Thai AF patients used warfarin with labile INR in each SAMeTT₂R₂ score.

Materials and Methods: The present retrospective study recruited Thai atrial fibrillation [AF] patients treated at the Central Chest Institute of Thailand. They took warfarin for at least three months before enrollment. The patients that discontinued warfarin during the international normalized ratio [INR] monitoring because of surgery, invasive procedure, hospitalization, or any etiologies were excluded. Each AF patients was measured for the INR to determine the proportion of patients with labile INR in each SAMeTT₂R₂ score.

Results: Forty AF patients were enrolled. The mean age was 64.35±10.69 years old. Most patients were paroxysmal AF. The average CHA₂DS₂-VASc score was 3.20±1.56. Half of these patients had hypertension and hypercholesterolemia. Almost one-fifth of these patients had history of ischemic stroke. The study showed the increased proportion of AF patients with labile INR according to the increased SAMeTT₂R₂ score. The AF patients with SAMeTT₂R₂ score of 3 or more had a closer proportion of patients with labile INR than those with SAMeTT₂R₂ score of 2 or less with borderline significance (p-value 0.056).

Conclusion: Thai AF patients with increased SAMeTT₂R₂ score had potential of having labile INR. However, a larger study is needed to use SAMeTT₂R₂ score for predicting Thai AF patients with labile INR in the future.

Keywords: Atrial fibrillation, Bleeding risk score, Anticoagulant, Labile INR, SAMeTT₂R₂