International guidelines recommend that an average individual time in therapeutic range should be >65% to 70% for optimal efficacy and safety outcomes while taking a vitamin K antagonist. The Sex, Age (<60 years); Medical history (at least 2 of the following: hypertension, diabetes, coronary artery disease/myocardial infarction, peripheral arterial disease, congestive heart failure, previous stroke, pulmonary disease, hepatic or renal disease); Treatment (interacting drugs, eg, amiodarone for rhythm control) [all 1 point]; and the current Tobacco use (2 points) and Race (non-Caucasian; 2 points) (SAMe-TT₂R₂) score would help decision making by identifying those patients with newly diagnosed atrial fibrillation who could do well on vitamin K antagonists. The study objective was to validate the predictive value of the SAMe-TT₂R₂ score for discriminating those who would achieve a high time in the therapeutic range (≥65%) in a prospective “real-world” cohort of patients with atrial fibrillation initiating oral anticoagulation therapy with vitamin K antagonists.

We studied an inception cohort of consecutive patients with nonvalvular atrial fibrillation who initiated oral anticoagulation in our outpatient anticoagulation clinic. The baseline SAMe-TT₂R₂ score was calculated. At 6 months, we calculated the time in therapeutic range using a linear method.

We included 459 patients, of whom 222 (47%) were male. Their median age was 76 years (interquartile range, 70-82 years), median Cardiac failure or dysfunction, Hypertension, Age over 75 years [Doubled], Diabetes, Stroke [Doubled] – Vascular disease, Age between 65-74 and Sex category [Female] (CHA₂DS₂-VASc) score was 4 (3-5), and median Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly (HAS-BLED) score was 3 (2-3). The median SAME-TT₂R₂ score was 2 (1-2). At 6 months, the mean ± standard deviation time in therapeutic range was 64% ± 17% overall, and 248 patients (54%) had a time in therapeutic range value >65%. Patients with a SAME-TT₂R₂ score 0 to 1 had a mean time in therapeutic range of 67% ± 18%, whereas patients with a SAME-TT₂R₂ score ≥2 had a mean time in therapeutic range of 61% ± 16% (P < .001). The odds ratio for having a low time in therapeutic range value was 2.10 (95% confidence interval, 1.44-3.06; P < .001) for those patients with a SAME-TT₂R₂ score ≥2.

In a prospective “real-world” inception cohort of patients with atrial fibrillation initiating oral anticoagulation with acenocoumarol, we have validated the clinical value of the SAME-TT₂R₂ score for the identification of patients who would have poor-quality anticoagulation. Thus, rather than imposing a “trial of vitamin K antagonists” for such patients (and exposing such patients to thromboembolic risks), we can a priori identify those patients who can (not cannot) do well on a vitamin K antagonists. Such patients would benefit from additional strategies for improving anticoagulation control with vitamin K antagonists or alternative oral anticoagulant drugs.