What is the PESI Score?
The Pulmonary Embolism Severity Index (PESI) is a validated clinical prediction tool that estimates 30-day mortality risk in patients with acute pulmonary embolism by incorporating 11 weighted clinical variables, primarily used to identify low-risk patients (Classes I and II) who are candidates for outpatient management. 1
Score Components and Calculation
The original PESI includes 11 variables with different point values: 1, 2
- Age = patient's age in years
- Male sex = +10 points
- Cancer = +30 points
- Chronic heart failure = +10 points
- Chronic pulmonary disease = +10 points
- Pulse rate ≥110 bpm = +20 points
- Systolic blood pressure <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
Risk Classification
The PESI stratifies patients into five mortality risk classes based on total points: 2
- Class I (≤65 points): 1.6% 30-day mortality - very low risk
- Class II (66-85 points): 3.5% 30-day mortality - low risk
- Class III (86-105 points): 7.1% 30-day mortality - intermediate risk
- Class IV (106-125 points): 11.4% 30-day mortality - intermediate-high risk
- Class V (≥126 points): 23.9% 30-day mortality - high risk
The score was derived and validated in 15,752 patients with confirmed PE, demonstrating excellent discriminatory power with area under the ROC curve of 0.77-0.87. 1
Simplified PESI (sPESI)
Due to the complexity of the original PESI, a simplified version uses 6 binary variables (1 point each): 1, 2
- Age >80 years
- Cancer (active, diagnosed within 12 months or undergoing treatment)
- Chronic cardiopulmonary disease
- Pulse ≥110 bpm
- Systolic blood pressure <100 mmHg
- Arterial oxygen saturation <90% (with or without supplemental oxygen)
A score of 0 indicates low risk (30-day mortality 1.0-1.1%), while ≥1 indicates higher risk. 3, 4 The sPESI classifies 30-36% of patients as low risk compared to 36-49% with the original PESI, though the original PESI has slightly better discriminatory power (AUC 0.78 vs 0.72). 5
Clinical Application for Risk Stratification
Low-risk patients (PESI Class I/II or sPESI=0) should be offered outpatient management when exclusion criteria are absent and a robust follow-up pathway exists. 1, 3, 6 These patients had 0-1.6% 30-day mortality with no major bleeding or recurrent VTE during follow-up in validation studies. 1
Intermediate-risk patients (PESI Class III or higher with sPESI ≥1) require inpatient management with further stratification based on right ventricular dysfunction and cardiac biomarkers. 6 However, research shows that 30-47% of patients classified as high-risk by PESI were safely managed as outpatients, suggesting the score may be overly conservative for some patients. 7
High-risk patients with hemodynamic instability require immediate inpatient management with consideration of thrombolysis regardless of PESI score. 6
Important Clinical Nuances
The PESI's principal strength lies in its high negative predictive value—reliably identifying patients at very low risk who can be safely managed as outpatients. 1 External validation confirmed 0% mortality in PESI Class I and 1.0% in Class II at 90 days, with no major bleeding or recurrent VTE. 1
A critical caveat: The presence of right ventricular dysfunction on imaging or elevated cardiac biomarkers should prompt further risk stratification even in low PESI/sPESI patients, as these findings may warrant inpatient observation. 2 Additionally, concomitant DVT is an adverse prognostic factor independently associated with 30-day mortality (OR 1.9), indicating significant comorbidity that may influence management decisions. 1, 6
For intermediate-risk patients initially classified as PESI Class III, recalculating the PESI at 48 hours can identify 27% who downgrade to low-risk status with only 1.2% 30-day mortality, potentially allowing earlier discharge. 8
Common Pitfalls to Avoid
Do not rely solely on RV dilation on imaging to exclude patients from outpatient management—measure cardiac biomarkers (BNP/troponin) for additional risk stratification if RV dilation is present. 6 Do not discharge patients without same-day anticoagulation initiated. 6 In cancer patients, these scores require additional clinical judgment as the original derivation studies included limited numbers of oncology patients. 2