title: Factors affecting quality of anticoagulation control among patients with atrial fibrillation on warfarin: the SAMe-TT₂R₂ score.
abstract: BACKGROUND
  When oral anticoagulation with adjusted-dose vitamin K antagonist (VKA) is used, the quality of anticoagulation control (as reflected by the time in therapeutic range [TTR] of the international normalized ratio [INR]) is an important determinant of thromboembolism and bleeding. Our objective was to derive a validated scheme using patient-related clinical parameters to assess the likelihood of poor INR control among patients with atrial fibrillation (AF) on VKA therapy.
  
  
  METHODS
  The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial population was randomly divided into derivation and internal validation cohorts using a 1:1 ratio. We used linear regression analysis to detect the clinical factors associated with 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.
  
  
  RESULTS
  In the linear regression model, nine variables emerged as independent predictors of TTR: female sex (P < .0001), age < 50 years (P < .0001), age 50 to 60 years (P = .02), ethnic minority status (P < .0001), smoking (P = .03), more than two comorbidities (P < .0001), and being treated with a β-blocker (P = .02), verapamil (P = .02), or, inversely, with amiodarone (P = .05). We 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, eg, 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% CI, 0.64-0.795; and c-index, 0.7; 95% CI, 0.57-0.82, respectively).
  
  
  CONCLUSIONS
  Common clinical and demographic factors can influence the quality of oral anticoagulation. We incorporated these 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-TT₂R₂ score = 0-1), or conversely, those who require additional interventions to achieve acceptable anticoagulation control (SAMe-TT₂R₂ score ≥ 2).
authors.affiliation: University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, England.
authors.forename: Stavros
authors.initials: S
authors.lastname: Apostolakis
authors.affiliation: Division of Cardiovascular Medicine University of Iowa Hospitals and Clinics, Iowa City, IA.
authors.forename: Renee M
authors.initials: RM
authors.lastname: Sullivan
authors.affiliation: Division of Cardiovascular Medicine University of Iowa Hospitals and Clinics, Iowa City, IA.
authors.forename: Brian
authors.initials: B
authors.lastname: Olshansky
authors.affiliation: University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, England. Electronic address: g.y.h.lip@bham.ac.uk.
authors.forename: Gregory Y H
authors.initials: GYH
authors.lastname: Lip
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage; D001281:Atrial Fibrillation / Q000150:complications* / Q000503:physiopathology; D001777:Blood Coagulation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019984:Quality Indicators, Health Care; D020521:Stroke / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D016896:Treatment Outcome; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D000925:Anticoagulants; D014859:Warfarin