Mehran Risk Score for Contrast-Induced Nephropathy Prediction
The Mehran risk score is the validated and recommended scoring system for predicting contrast-induced nephropathy (CIN) in patients undergoing percutaneous coronary intervention, particularly those with pre-existing kidney disease, diabetes, and heart failure. 1
Components of the Mehran Risk Score
The Mehran score incorporates eight clinical and procedural variables to stratify CIN risk 1:
- Hypotension (systolic BP <80 mmHg for at least 1 hour requiring inotropic support or intra-aortic balloon pump within 24 hours peri-procedurally) 2
- Intra-aortic balloon pump use 2
- Congestive heart failure (NYHA class III/IV or history of pulmonary edema) 3
- Age >75 years 2
- Anemia (baseline hematocrit <39% for men, <36% for women) 4
- Diabetes mellitus 5
- Contrast media volume 5
- Chronic kidney disease (baseline serum creatinine >1.5 mg/dL or eGFR <60 mL/min/1.73m²) 1, 6
Risk Stratification Categories
The score categorizes patients into four risk groups 2, 5:
- Low risk: Score ≤5 (CIN risk ~7.5%)
- Moderate risk: Score 6-10 (CIN risk ~14%)
- High risk: Score 11-15 (CIN risk ~26%)
- Very high risk: Score ≥16 (CIN risk ~57%)
Clinical Validation and Prognostic Value
The Mehran score predicts not only CIN development but also short- and long-term mortality and major adverse cardiovascular events. 2 In ST-elevation myocardial infarction patients undergoing primary PCI, mortality in the very high-risk group was more than 10-fold higher (HR 10.11,95% CI 4.83-21.1) compared to the low-risk group 2. The score maintains excellent discriminatory capacity with C-statistic values >0.8 and good calibration (Hosmer-Lemeshow p=0.7) in contemporary cohorts 5.
The score has been validated across multiple clinical settings including acute coronary syndromes 5, primary PCI for STEMI 2, and transcatheter aortic valve implantation 7, demonstrating consistent predictive accuracy over the past decade 5.
Alternative Simplified Approach
For rapid bedside assessment, the contrast volume-to-eGFR ratio (CV/GFR) provides comparable predictive accuracy to the Mehran score with greater simplicity. 4 A CV/GFR ratio >3.7 substantially increases CIN risk, particularly in patients with pre-existing renal impairment or diabetes 6. The CV/GFR ratio demonstrated similar area under the curve (0.79) compared to the Mehran score (0.65) in older adults undergoing coronary procedures 4.
Critical Caveats
Baseline chronic kidney disease remains the single most important risk factor, with patients having serum creatinine >2 mg/dL experiencing a 22.4% CIN incidence compared to 2.4% in those with normal function 6. Do not rely solely on baseline creatinine without calculating eGFR, as creatinine alone underestimates renal dysfunction, particularly in elderly patients and those with reduced muscle mass 3.
The score identifies patients requiring aggressive prophylactic measures including isotonic saline hydration (1.0-1.5 mL/kg/hour) for 3-12 hours before and 6-24 hours after contrast exposure, contrast volume minimization to <350 mL or <4 mL/kg, and use of low-osmolar or iso-osmolar contrast media 1, 3.