SAMe-TT₂R₂ Score

SAMe-TT₂R₂ Score

The SAMe-TT₂R₂ Score is a validated tool used to predict the quality of anticoagulation control with warfarin therapy, specifically the Time in Therapeutic Range (TTR). This score helps clinicians identify patients who may have difficulty maintaining therapeutic INR levels and guides decisions about anticoagulation strategy.

Scoring Criteria

The SAMe-TT₂R₂ Score assigns points based on patient characteristics that affect warfarin control:

Risk Factor	Points
Sex (Female)	+1
Age < 60 years	+1
Medical history (≥2 comorbidities)	+1
Treatment (interacting drugs)	+1
Tobacco use (within 2 years)	+2
Race (non-Caucasian)	+2

Risk Stratification and Expected TTR

Score	Risk Level	Expected TTR	Clinical Implication
0-1	Low	72.8%	Good warfarin control expected
2	Medium	66.2%	Moderate warfarin control
≥3	High	58.0%	Poor warfarin control expected

Time in Therapeutic Range (TTR) Calculation

TTR is calculated using the Rosendaal method, which provides a linear interpolation of INR values:

For atrial fibrillation, the therapeutic INR range is typically 2.0-3.0.

Clinical Application and Management

The SAMe-TT₂R₂ Score helps guide anticoagulation decisions:

• Low Risk (0-1 points):
  • Expected TTR: 72.8%
  • Standard warfarin management is likely to be effective
  • Routine INR monitoring is appropriate
• Medium Risk (2 points):
  • Expected TTR: 66.2%
  • Consider more frequent INR monitoring
  • Enhanced patient education and adherence strategies
  • Consider warfarin management clinics
• High Risk (≥3 points):
  • Expected TTR: 58.0%
  • Consider alternative anticoagulants (DOACs)
  • If warfarin is continued, intensive management required
  • Frequent INR monitoring and dose adjustments
  • Consider specialized anticoagulation clinics

Comparison with DOACs

For patients with high SAMe-TT₂R₂ scores (≥3), DOACs may be preferred:

• Advantages of DOACs in high-risk patients:
  • No need for INR monitoring
  • Fewer drug interactions
  • More predictable pharmacokinetics
  • Better adherence potential
• Considerations:
  • Cost and insurance coverage
  • Renal function (affects DOAC dosing)
  • Patient preference
  • Contraindications to DOACs

Important Considerations

The SAMe-TT₂R₂ Score should be used as part of a comprehensive clinical assessment:

• It is specifically validated for atrial fibrillation patients
• The score predicts TTR but does not guarantee outcomes
• Individual patient factors may influence decision-making
• Regular reassessment may be needed as patient factors change
• Consider patient preferences and values in shared decision-making
• Follow institutional protocols and guidelines

Validation and Performance

The SAMe-TT₂R₂ Score has been extensively validated:

• Discrimination: Good ability to distinguish between patients with good vs. poor warfarin control
• Calibration: Well-calibrated across different populations
• External validation: Validated in multiple cohorts
• Clinical utility: Shown to improve anticoagulation decision-making

This tool has been widely adopted in clinical practice and is recommended by major guidelines for anticoagulation management in atrial fibrillation.