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PERC rule for pulmonary embolism
Rules out PE in low-probability patients without further testing.
PERC rule for pulmonary embolism
Age ≥50 years
Heart rate ≥100 /min
O₂ saturation <95 % on room air
Haemoptysis
Oestrogen use
Prior DVT or PE
Recent surgery or trauma (≤4 weeks, needing hospitalisation)
Unilateral leg swelling
ResultPERC negative
All eight criteria absent — in a patient already judged low pre-test probability, PE can be excluded without D-dimer or imaging (<2 % risk).
When to use
- Only in patients you have already judged to be at low clinical (gestalt) pre-test probability of PE. PERC is not valid in moderate- or high-probability patients.
Formula
PE can be excluded when all eight are absent: age ≥50, HR ≥100, SpO₂ <95%, haemoptysis, oestrogen use, prior VTE, recent surgery/trauma, unilateral leg swelling.
Pearls and pitfalls
- Applying PERC to a patient who is not low pre-test probability re-introduces the missed diagnoses it was designed to avoid — the two steps are sequential.