Validation of the SAMe-TT2R2 score in a nationwide population of nonvalvular atrial fibrillation patients on vitamin K antagonists

The SAMe-TT2R2 score has been proposed to identify patients with non valvular atrial fibrillation (AF) who maintain a high average time in therapeutic range (TTR) on vitamin K antagonists treatment (VKA). This score has been validated in several studies, either monocentric or including very selected populations in a specialised setting. Our objective was to validate this score in a nationwide cohort of AF patients. From November 2013 to March 2014 we included in this study the first 10 patients with AF on VKA consecutively seen in 120 outpatient cardiology clinics in Spain. The SAMe-TT2R2 score was calculated for each patient and TTR in the preceding six months was estimated by Rosendaal method. A total of 1,056 patients were recruited (mean age 73.6 +/- 9.8 years, 42% female). Mean value of TTR was 63.8 +/- 25.9% (median 66.8 %, interquartile range 45.6 %-85.4 %). We found a progressive decline in mean TTR from a score of 0 (67.5% +/- 24.6%) to >= 4 (52.7 +/- 28.7%, p<0.01). The score was able to discriminate which patients had a good anticoagulation control (TTR >= 65%) with a C-statistic of 0.57 (95%C10.53-0.60, p< 0.0005). A SAMe-TT2R2 score of 0-1 was associated with a good anticoagulation control with a sensitivity, specificity, positive and negative predictive values of 64%, 48%, 58% and 54%, respectively; and the odds ratio of having a TTR< 65% if the score was >= 2 was 1.64 (95% confidence interval 1.33-1.95, p<0.001). In conclusion, in this nationwide population with AF on VKA, the SAMe-TT2R2 score had a significant, although moderate, ability to identify patients with a good anticoagulation control.