PERC rule for pulmonary embolism
Rules out PE without testing in low-pretest-probability patients.
Inputs
Age 50 or older
Heart rate 100 or higher
SaO₂ below 95% on room air
Unilateral leg swelling
Hemoptysis
Surgery or trauma within 4 weeks
Prior PE or DVT
Hormone useOral contraceptives, hormone replacement, or estrogen
Worked calculation
Your values are highlighted.
- Points
When to use
- Only when clinical gestalt puts PE risk below about 15%.
Pearls and pitfalls
- Do not apply to moderate or high pretest probability.
Why use
Clear yes or no.
| Criterion | Points |
|---|---|
| Age 50 or older | +1 |
| Heart rate 100 or higher | +1 |
| SaO₂ below 95% on room air | +1 |
| Unilateral leg swelling | +1 |
| Hemoptysis | +1 |
| Surgery or trauma within 4 weeks | +1 |
| Prior PE or DVT | +1 |
| Hormone use | +1 |
In a low-pretest-probability patient, PE can be ruled out without further testing.