🫁 PERC Rule (PE Rule-out Criteria)
Apply the PERC rule to exclude pulmonary embolism without D-dimer in low-risk patients.
PERC Rule (PE Rule-out Criteria)
Age ≥ 50
Heart rate ≥ 100
SpO₂ < 95%
Haemoptysis
Oestrogen use
Prior DVT/PE
Unilateral leg swelling
Surgery/trauma ≤ 4 weeks (needing hospitalisation)
When to use
Rule out PE when clinical pre-test probability is already low.
How it works
Eight criteria (age ≥ 50, HR ≥ 100, SpO₂ < 95%, haemoptysis, oestrogen, prior DVT/PE, unilateral leg swelling, surgery/trauma ≤ 4 weeks). If all are negative, PE is excluded.
Key points
- Only valid in low pre-test-probability patients.
- Any positive criterion means PERC fails — proceed with workup.
- Avoids unnecessary D-dimer testing.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.