PERC Rule Calculator
Calculate Pulmonary Embolism Risk using the PERC Rule. Assess probability of PE in low-risk patients to guide clinical decision-making.
Step 1: Patient Assessment
PERC Rule Criteria
Check ALL criteria. If ANY are POSITIVE, PERC Rule is POSITIVE and PE cannot be ruled out.
Step 2: Clinical Context
PERC Rule Interpretation
• PERC NEGATIVE (All criteria negative): PE risk <2% in low-risk patients
• PERC POSITIVE (Any criterion positive): Requires further evaluation
• Use only in patients with low clinical suspicion
Clinical Notes
PERC Rule validated for emergency department use. Not for use in pregnant patients, inpatients, or those with high clinical suspicion.
PERC Rule Results
PERC Rule Result
Clinical Guidelines
PERC Rule Application
Indications:
• Emergency department patients with suspected PE
• Low clinical suspicion based on gestalt
• Outpatients with unexplained dyspnea or chest pain
Contraindications:
• High clinical suspicion
• Inpatients
• Pregnant patients
• Patients with active cancer
• Known thrombophilia
Management Algorithm
| PERC Result | Pretest Probability | Recommendation |
|---|---|---|
| Negative | Low | PE ruled out, no further testing |
| Positive | Low | D-dimer testing |
| Any | Moderate/High | Imaging (CTPA or V/Q scan) |
Evidence & Validation
Validation Studies
Original Validation Study (2004):
• Sensitivity: 97.4%
• Specificity: 21.9%
• NPV: 99.5% in low-risk patients
• Prevalence: 8% in study population
Multicenter Prospective Study (2008):
• Failure rate: 1.0% (95% CI 0.6-1.6)
• 95% sensitivity
• Safe for clinical use
Performance Characteristics
| Parameter | Value | 95% CI |
|---|---|---|
| Sensitivity | 97.4% | 94.8-98.9% |
| Specificity | 21.9% | 19.4-24.5% |
| Negative Predictive Value | 99.5% | 98.0-99.9% |
| Positive Predictive Value | 9.2% | 7.8-10.8% |
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