PESI Score: Risk Stratification Tool for Acute Pulmonary Embolism
The Pulmonary Embolism Severity Index (PESI) is the most extensively validated clinical prediction rule for risk-stratifying patients with acute PE, with its primary strength being the reliable identification of low-risk patients (PESI classes I-II) who are candidates for outpatient management, demonstrating a negative predictive value exceeding 98% for 30-day mortality. 1
What the PESI Score Is
The PESI integrates 11 clinical variables that combine PE severity markers with patient comorbidities to predict 30-day all-cause mortality. The score stratifies patients into five risk classes (I-V) with progressively increasing mortality risk 1.
Original PESI Components (11 variables):
- Age: Actual age in years (not points)
- Male sex: +10 points
- Cancer: +30 points
- Chronic heart failure: +10 points
- Chronic pulmonary disease: +10 points
- Pulse rate ≥110 bpm: +20 points
- Systolic BP <100 mmHg: +30 points
- Respiratory rate >30 breaths/min: +20 points
- Temperature <36°C: +20 points
- Altered mental status: +60 points
- Arterial oxygen saturation <90%: +20 points 1
Simplified PESI (sPESI) - 6 variables (1 point each):
- Age >80 years
- Cancer
- Chronic pulmonary disease
- Pulse rate ≥110 bpm
- Systolic BP <100 mmHg
- Arterial oxygen saturation <90% 1
How to Use PESI Clinically
Risk Classification Algorithm:
Step 1: Calculate the score using all available clinical data at presentation
Step 2: Classify risk level:
- Low-risk: PESI classes I-II (original) or sPESI = 0 points
- High-risk: PESI classes III-V (original) or sPESI ≥1 point 1
Step 3: Make disposition decision:
- Low-risk patients: Consider outpatient management or early discharge (mortality <1.1%) 2
- High-risk patients: Require hospitalization for monitoring and treatment 1
Clinical Performance
The PESI demonstrates exceptional accuracy for identifying low-risk patients:
- Sensitivity for mortality: 89.5-94.1% 3
- Negative predictive value: >98% 3, 4
- No deaths observed in PESI classes I-III in validation studies 5
- Class V mortality: 9.2% at 30 days, 10.5% at 90 days 5
Recent comparative analyses confirm PESI as the superior prognostic tool, outperforming modified Bova, FAST, CPES, and other scores with an AUC of 0.84 for predicting PE-related adverse outcomes 4.
Critical Clinical Considerations
Strengths:
- Most extensively validated across multiple international cohorts 1, 6, 2
- Proven safe in randomized trials for guiding outpatient management 1
- High reproducibility with good inter-rater reliability (kappa = 0.69) 5
- sPESI offers practical simplicity while maintaining excellent negative predictive value 3
Important Caveats:
The PESI identifies who is low-risk, not who requires admission. Studies show 30-47% of patients classified as high-risk by PESI were safely managed as outpatients, indicating the score is conservative 7. Use clinical judgment for borderline cases.
PESI predicts all-cause mortality, not just PE-related death. The score incorporates comorbidity burden, making it particularly useful for overall risk assessment but potentially over-triaging patients with significant comorbidities who have small PEs 1.
Despite guideline recommendations since 2014, PESI remains underutilized in clinical practice, with many low-risk patients unnecessarily hospitalized 6.
Integration with ESC Risk Stratification
The 2019 ESC Guidelines incorporate PESI/sPESI as the foundation for identifying low-risk PE:
- Low-risk PE: Hemodynamically stable + negative PESI/sPESI + negative imaging/biomarkers (optional assessment) 1
- Intermediate-low risk: Positive PESI/sPESI + one or no positive cardiac markers
- Intermediate-high risk: Positive PESI/sPESI + both RV dysfunction and positive troponin 1
For low-risk patients identified by PESI classes I-II or sPESI = 0, outpatient management is safe and recommended, with mortality rates consistently <1.1% across validation studies 1, 2, 7.