Factors Affecting Quality of Anticoagulation Control Among Patients With Atrial Fibrillation on Warfarin: The SAMe-TT2R2 Score

Study Questions:

What is the utility of a validated scheme using patient-related clinical parameters to assess the likelihood of poor international normalized ratio (INR) control among patients with atrial fibrillation (AF) on vitamin K antagonist (VKA) therapy?


The AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management) trial population was randomly divided into derivation and internal validation cohorts using a 1:1 ratio. The investigators used linear regression analysis to detect the clinical factors associated with time in therapeutic range (TTR), and binary logistic regression to evaluate the predictive performance of a model incorporating these factors for different cutoff values of TTR. The derived model was validated externally in a cohort of patients receiving anticoagulant therapy who were recruited prospectively.


In the linear regression model, nine variables emerged as independent predictors of TTR: female sex (p < 0.0001), age <50 years (p < 0.0001), age 50-60 years (p = 0.02), ethnic minority status (p < 0.0001), smoking (p = 0.03), more than two comorbidities (p < 0.0001), and being treated with a beta-blocker (p = 0.02), verapamil (p = 0.02), or, inversely, with amiodarone (p = 0.05). The investigators incorporated these factors into a simple clinical prediction scheme with the acronym SAMe-TT2R (sex female, age <60 years, medical history [more than two comorbidities], treatment [interacting drugs, e.g., amiodarone for rhythm control], tobacco use [doubled], race [doubled]). The score demonstrated good discrimination performance in both the internal and external validation cohorts (c-index, 0.72; 95% confidence interval, 0.64-0.795; and c-index, 0.7; 95% confidence interval, 0.57-0.82, respectively).


The authors concluded that common clinical and demographic factors can influence the quality of oral anticoagulation.


The investigators incorporated common clinical and demographic factors into a simple score (SAMe-TT2R2) that can predict poor INR control and aid decision-making by identifying those patients with AF who would do well on VKA (SAMe-TT22 score = 0-1), or conversely, those who require additional interventions to achieve acceptable anticoagulation control (SAMe-TT2R2 score ≥2). This score can be considered when making therapeutic decisions, including the choice of novel oral anticoagulants as an alternative to warfarin, and appears to be of special value in an era of limited resources because it may provide useful information for improving the safety and effectiveness of antithrombotic prophylaxis, without the need for sophisticated genotype-phenotype characterizations. Apart from suggesting an alternative option to warfarin, predicting a poor TTR before starting treatment with a VKA may also be the basis for a more focused follow-up and more comprehensive control of patient compliance and education.

Clinical Topics: Anticoagulation Management

Keywords: Vitamin K, Ethnic Groups, Follow-Up Studies, Continental Population Groups, Warfarin, Blood Coagulation, Cardiology, Genotype, Tobacco Use, Tobacco Use Disorder

< Back to Listings