ToolsCalculators
Altitude-adjusted PERC rule
PERC rule using a lower oxygen-saturation threshold for altitude.
Altitude-adjusted PERC rule
Age >= 50 years
Heart rate >= 100 /min
Oxygen saturation < 90% (altitude-adjusted)
Unilateral leg swelling
Hemoptysis
Recent surgery or trauma (within 4 weeks, requiring hospitalization)
Prior PE or DVT
Hormone use (estrogen)
ResultPERC negative
No criteria met: in a patient already judged low pretest probability, PE can be excluded without D-dimer or imaging.
- Criteria positive
- 0
When to use
- Excluding PE in low-probability patients at high altitude, where a 90% saturation threshold reduces false-positive rule-outs.
Formula
Eight criteria; PERC is negative only if none are present. The altitude-adjusted version uses oxygen saturation <90% (instead of <95%) as the hypoxia criterion.
Pearls and pitfalls
- PERC only applies after gestalt has already established low pretest probability; it is a rule-out, not a rule-in, tool.