What are the reference values for the Mayo surgical risk score?

Reference Values of Mayo Surgical Risk Score

The Mayo Clinic Risk Score (MCRS) for surgical risk stratification ranges from 0 to 24 points, with scores categorized as very low risk (<5), low risk (6-8), moderate risk (9-11), high risk (12-14), and very high risk (15-25), corresponding to increasing mortality risk.

Mayo Clinic Risk Score Components

The Mayo Clinic Risk Score is based on seven pre-procedure variables that predict surgical mortality and complications:

1. Age
2. Serum creatinine/renal function
3. Ejection fraction
4. Myocardial infarction within 24 hours
5. Presence of shock
6. Congestive heart failure
7. Peripheral vascular disease

Risk Stratification and Mortality Correlation

The MCRS demonstrates strong correlation with observed mortality:

• Very Low Risk (MCRS <5): 0-0.3% mortality 1
• Low Risk (MCRS 6-8): 0.9% mortality 1
• Moderate Risk (MCRS 9-11): 3.2% mortality 1
• High Risk (MCRS 12-14): 10.7% mortality 1
• Very High Risk (MCRS 15-25): 25.1-33.8% mortality 2, 1

Validation and Performance

The MCRS has been extensively validated across multiple surgical populations:

• In percutaneous coronary intervention (PCI), it demonstrates excellent discrimination with an area under the receiver operating characteristic curve (AUC) of 0.76 3
• In coronary artery bypass graft (CABG) surgery, it shows moderate discriminatory ability with AUC ranging from 0.715 to 0.784 2
• For primary angioplasty, it demonstrates strong predictive value with an overall c-statistic of 0.85 1

Clinical Applications

The MCRS has several important clinical applications:

1. Pre-procedure Risk Assessment: Provides individualized mortality risk estimates before surgical intervention
2. Informed Consent: Helps communicate evidence-based risk estimates to patients
3. Resource Allocation: Identifies high-risk patients who may benefit from more intensive monitoring
4. Quality Improvement: Allows for risk-adjusted outcomes assessment

Limitations and Considerations

When applying the MCRS, consider these important caveats:

• Performance may vary by surgical population and procedure type
• While validated for cardiovascular procedures, application to other surgical specialties may require additional validation
• The MCRS performs better for short-term mortality prediction than for long-term outcomes
• The score should be calculated using pre-procedure variables only

Special Populations

In specific patient groups, the MCRS maintains its predictive value:

• Even when excluding patients with cardiogenic shock (10.5% of patients in validation studies), the higher MCRS categories still predicted increased mortality risk 1
• The score demonstrates good performance across age groups, though advanced age (>85 years) itself carries a 6.24 times higher risk of complications 4

The MCRS provides a validated, practical tool for surgical risk stratification that can guide clinical decision-making and improve patient outcomes through appropriate risk assessment.