Healthcare & Clinical Formulas
SAMe-TT2R2 Score: Warfarin INR Quality (TTR) vs Upfront DOAC Selection
Calculate Stavros Apostolakis’ 0–8 SAMe-TT2R2 anticoagulation choice score (Sex female +1, Age <60 +1, Medical history >2 comorbidities +1, Interacting Rx like amiodarone +1, Tobacco within 2 yrs +2, Non-Caucasian Race +2) to predict poor warfarin INR control.
Predicting poor warfarin INR control BEFORE a "trial of warfarin" causes stroke or bleed!
Warfarin protects against atrial fibrillation stroke ONLY when Time in Therapeutic Range (TTR, INR 2.0–3.0) stays >= 65%–70%. Historically, clinicians subjected patients to a risky multi-month "trial of warfarin" just to discover erratic INRs! Stavros Apostolakis, Gregory Lip, et al. (Chest, 2013) derived the clinical acronym SAMe-TT_2R_2 (0–8 points): Sex female (+1), Age < 60 years (+1), Medical history (>2 of HTN, diabetes, CAD/MI, PAD, HF, prior stroke, pulmonary, hepatic, or renal disease: +1), Treatment with rhythm-interacting drugs like amiodarone (+1), Tobacco use within 2 years (doubled: +2), and Race non-Caucasian (doubled: +2)!
Patients scoring 0–2 points reliably achieve good warfarin TTR (>= 65–70%) when VKA therapy is considered, whereas patients scoring >= 3 points have high probability of labile TTR and should receive an upfront Direct Oral Anticoagulant (DOAC) or intensive INR clinic management!
| SAMe-TT2R2 Total Score (0–8) | Expected Warfarin TTR Quality | Anticoagulant Selection Guidance |
|---|---|---|
| 0 – 2 Points (e.g., Female +1, >2 Comorbidities +1) | Likely Favorable TTR (>=65–70%) | VKA Acceptable if Indicated (or DOAC) |
| >= 3 Points (e.g., Smoker +2, Amiodarone +1 = 3) | Suboptimal / Labile INR Likely | Prefer Upfront DOAC (Avoid Trial of Warfarin!) |
| Non-Binary Entry (!= 0 or 1) | Validation Guard | "Invalid Binary SAMe-TT2R2 Flag" |
Weighted 6-Item SAMe-TT2R2 Score (0–8)
Sums 1-point items B2:B5 and doubled 2-point items 2*B6 (Tobacco) + 2*B7 (Non-Caucasian Race).
=IF(OR(COUNTA(B2:B7) < 6, SUMPRODUCT((B2:B7 <> 0) * (B2:B7 <> 1)) > 0), "Invalid Binary SAMe-TT2R2 Flag", B2 + B3 + B4 + B5 + 2 * B6 + 2 * B7)Warfarin TTR Prediction & DOAC Recommendation (>= 3 Cutoff)
Recommends upfront DOAC (or intensive INR support) at SAMe-TT2R2 >= 3 vs favorable VKA TTR likelihood at 0–2.
=IF(OR(COUNTA(B2:B7) < 6, SUMPRODUCT((B2:B7 <> 0) * (B2:B7 <> 1)) > 0), "Invalid Binary SAMe-TT2R2 Flag", IF(B2 + B3 + B4 + B5 + 2 * B6 + 2 * B7 >= 3, "Poor Expected Warfarin TTR (>=3: Prefer Upfront DOAC)", "Likely Good Warfarin TTR (0-2: TTR >=65-70% Achievable)"))Try the example
Use the original values or change them to test your understanding.