Cardiology
SAMe-TT₂R₂ Score
Predicts anticoagulation control on warfarin.
Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.
Background
The SAMe-TT₂R₂ score predicts how well a patient with atrial fibrillation (AF) is likely to maintain good anticoagulation control on a vitamin-K antagonist (VKA) such as warfarin, expressed as time in therapeutic range (TTR). It is used at the point of choosing therapy to identify people who may struggle to stay in range and might therefore be better served by a direct oral anticoagulant (DOAC). The components are: female Sex (1), Age <60 (1), Medical history of ≥2 comorbidities (1), interacting Treatment such as amiodarone (1), Tobacco use within two years (2) and non-white Race (2), giving a maximum of 8.
Interpreting the result
A score of 0–2 predicts that good VKA control (a high TTR) is likely, so a vitamin-K antagonist is a reasonable choice if a DOAC is not preferred. A score of 3 or more predicts poorer anticoagulation control and a lower TTR, and should prompt consideration of a DOAC, or — if a VKA is still used — more intensive INR monitoring and education. The score informs the choice of agent; it does not estimate stroke or bleeding risk.
Worked example
A 54-year-old white man who smokes and takes amiodarone scores: Age <60 (1) + Tobacco (2) + interacting drug (1) = 4. A score of 4 predicts poor warfarin control, so a DOAC would generally be favoured if otherwise appropriate.
Pearls / pitfalls
- It predicts quality of warfarin control, not stroke or bleeding risk — use CHA₂DS₂-VASc and a bleeding assessment for those.
- A high score is a prompt to consider a DOAC or intensify monitoring, not an absolute contraindication to a VKA.
- Predictive performance is modest; clinical judgement, adherence and access to monitoring also drive real-world TTR.
- The race and tobacco items carry the heaviest weighting, so they strongly influence whether a patient crosses the ≥3 threshold.
Evidence & validation
Derived by Apostolakis and colleagues from the AFFIRM and SPORTIF trial populations and validated in subsequent AF cohorts, where higher scores were associated with lower time in therapeutic range. It is referenced in several anticoagulation and AF management resources as an aid to VKA-versus-DOAC selection.
Frequently asked questions
What does a high SAMe-TT₂R₂ score mean?
A score of 3 or more predicts that the patient is less likely to maintain a good time in therapeutic range on warfarin. This favours a direct oral anticoagulant, or closer INR monitoring if a vitamin-K antagonist is still chosen.
Does it tell me the stroke risk?
No. SAMe-TT₂R₂ only predicts the quality of anticoagulation control on a VKA. Stroke risk in AF is assessed separately, usually with CHA₂DS₂-VASc.
Why are tobacco and race weighted two points?
In the derivation cohorts these factors were the strongest predictors of poor anticoagulation control, so they were assigned a higher weight. This means they have a large effect on whether the score reaches the ≥3 threshold.
Should a high score stop me using warfarin?
No. It simply flags a higher chance of poor control. Many patients with a high score can still do well on warfarin with good education and monitoring, but a DOAC is often a reasonable alternative.
References
- Apostolakis S, Sullivan RM, Olshansky B, Lip GYH. Factors affecting quality of anticoagulation control among patients with atrial fibrillation on warfarin: the SAMe-TT₂R₂ score. Chest. 2013;144(5):1555–1563.
- Hindricks G, et al. 2020 ESC Guidelines for the diagnosis and management of atrial fibrillation. Eur Heart J. 2021.
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