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Pulmonary Embolism Rule-Out Criteria (PERC) for identifying patients in whom PE can be safely ruled out without further testing when clinical pre-test probability is low.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
The PERC rule is applied to patients with a low pre-test probability of PE (e.g., Wells score <4). If all eight criteria are met, PE can be considered ruled out without D-dimer or imaging. It must not be used in patients with intermediate or high pre-test probability.
Specialty
Emergency MedicineCategory
EmergencyDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-15
Formula
Keywords
Normal Range
8/8 criteria met
Determines whether pulmonary embolism can be safely ruled out in a patient with low pre-test probability, without D-dimer or imaging.
The PERC rule counts how many of eight criteria are met (age under 50, heart rate under 100, oxygen saturation 95% or higher, no hemoptysis, no estrogen use, no prior DVT/PE, no unilateral leg swelling, no recent surgery/trauma). When all 8 criteria are met (PERC negative) PE can be considered ruled out in a patient with low pre-test probability.
Select Yes when age is under 50; Yes counts as one criterion met.
Select Yes when heart rate is under 100 bpm; Yes counts as one criterion met.
Select Yes when SpO2 is 95% or higher on room air; Yes counts as one criterion met.
Select Yes when there is no hemoptysis; Yes counts as one criterion met.
Select Yes when there is no estrogen use; Yes counts as one criterion met.
Select Yes when there is no prior DVT or PE; Yes counts as one criterion met.
Select Yes when there is no unilateral leg swelling; Yes counts as one criterion met.
Select Yes when there has been no recent surgery or trauma; Yes counts as one criterion met.
8/8 criteria met: PERC negative, PE can be ruled out without further testing. Fewer than 8/8: PERC positive, proceed with D-dimer and/or imaging.
The PERC rule safely reduces unnecessary D-dimer testing and CT pulmonary angiography in low-risk patients, lowering cost and radiation exposure without missing clinically significant PE.
A 35-year-old woman with pleuritic chest pain has HR 88 bpm, SpO2 97% on room air, no hemoptysis, no estrogen use, no prior DVT/PE, no leg swelling, and no recent surgery or trauma.
Inputs:
Expected Result: All 8 PERC criteria met — PERC negative. PE can be considered ruled out without D-dimer or imaging given the low pre-test probability.
All 8 criteria met (PERC negative): PE can be safely ruled out without D-dimer or imaging. Fewer than 8 met (PERC positive): proceed with D-dimer and/or CT pulmonary angiography.
Only in adult emergency patients with low pre-test probability of PE (typically Wells 4 or less or gestalt low). Do not use in patients with intermediate or high pre-test probability.
No. The original PERC derivation excluded pregnant patients. Use pregnancy-specific PE assessment pathways instead.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. The PERC rule applies only to patients with a low pre-test probability of PE and does not replace clinical judgment.