SAMe-TT₂R₂ Score for Anticoagulation Therapy Selection
The SAMe-TT₂R₂ score predicts which patients with atrial fibrillation are likely to achieve good time in therapeutic range (TTR) on warfarin, helping guide the choice between warfarin and DOACs.
About
The SAMe-TT₂R₂ score (Sex, Age, Medical history, Treatment, Tobacco use, Race) was developed by Apostolakis et al. and published in Chest in 2013. It predicts time in therapeutic range (TTR) in AF patients on warfarin. Score 0-2 indicates likely good TTR (≥65-70%), suitable for warfarin. Score ≥3 predicts poor TTR, suggesting DOAC may be preferred. Components: female sex (1), age ≥60 (1), ≥2 comorbidities (1, e.g., hypertension, diabetes, CAD, PAD, HF, stroke, pulmonary, hepatic, renal), interacting drugs (1, e.g., amiodarone, SSRIs, NSAIDs, statins), current smoker (2), non-Caucasian race (2).
Formula
Female (1) + Age ≥60 (1) + ≥2 Comorbidities (1) + Interacting Drugs (1) + Smoker (2) + Non-Caucasian (2)
The SAMe-TT₂R₂ score sums six variables: female sex (S=1 point), age ≥60 years (A=1 point), ≥2 medical comorbidities including hypertension, diabetes, CAD, PAD, HF, stroke, pulmonary, hepatic, or renal disease (Me=1 point), treatment with interacting drugs such as amiodarone, SSRIs, NSAIDs, or statins (T=1 point), tobacco use within 2 years (T₂=2 points), and non-Caucasian race (R₂=2 points). Total score 0-8. Score 0-2: likely good TTR (≥65%) — suitable for warfarin. Score ≥3: predicts poor TTR and higher risk of thromboembolism and bleeding — consider DOAC.
Score Interpretation
The SAMe-TT₂R₂ score helps clinicians choose between warfarin and DOACs. A score ≥3 identifies patients likely to have poor INR control on warfarin (TTR <65%), who may benefit from DOAC therapy. It complements CHA₂DS₂-VASc and HAS-BLED in the anticoagulation decision pathway.
Suitable for Warfarin — 0–2
Likely good TTR (≥65%). Suitable for warfarin therapy with routine monitoring.
Management: Initiate warfarin with routine INR monitoring. Target INR 2.0-3.0.
Not Ideal for Warfarin — Consider DOAC — 3–8
Predicted poor TTR (<65%). Higher risk of complications on warfarin.
Management: Consider DOAC instead of warfarin. If warfarin required, more frequent monitoring and consider anticoagulation clinic referral.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| AF patients considered for anticoagulation | 0-8 points | Score 0-2: good TTR expected. Score ≥3: poor TTR expected — consider DOAC. |
Dr. Khaled Hassan
Dr. Khaled is a cardiology consultant with experience in managing cardiovascular patients.
View medical review board & editorial policy →Example Calculation
A 65-year-old Asian woman with AF, hypertension, and diabetes, on amiodarone, non-smoker. SAMe-TT₂R₂: female (1) + age ≥60 (1) + ≥2 comorbidities (1) + interacting drugs (1) + non-smoker (0) + non-Caucasian (2) = 6/8. Score ≥3 — poor TTR predicted on warfarin. Consider DOAC.
Related Conditions
Related Medications
Common Mistakes
Using SAMe-TT₂R₂ as a bleeding risk score
SAMe-TT₂R₂ predicts TTR quality on warfarin, not bleeding risk. Use HAS-BLED for bleeding risk assessment.
Counting smoking as 1 point instead of 2
Current smoking (within 2 years) scores 2 points — the highest weighted variable in the score.
Frequently Asked Questions
What TTR threshold does SAMe-TT₂R₂ predict?
Should a high SAMe-TT₂R₂ score preclude warfarin use?
References
- Apostolakis S, Sullivan RM, Olshansky B, et al. Factors affecting quality of anticoagulation control among patients with atrial fibrillation on warfarin: the SAMe-TT₂R₂ score. Chest. 2013;144(5):1555-1563. PubMed
- Zulkifly H, Lip GYH, Lane DA. Use of the SAMe-TT₂R₂ score to predict anticoagulation control in atrial fibrillation and venous thromboembolism: a systematic review and meta-analysis. Heart. 2018;104(16):1339-1345. PubMed