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PERC Rule for PE

Stops the PE workup before it starts — but only in a patient you have ALREADY judged low-risk.

PERC negative — PE ruled out
No criteria met · <1.8% miss rate
No D-dimer needed — but ONLY if pretest probability is genuinely low (Wells <2)
0pts
Age ≥50 years
Heart rate ≥100 bpm
O₂ saturation <95% on room air
Unilateral leg swelling
Hemoptysis
Recent surgery or trauma requiring hospitalization within 4 weeks
Prior PE or DVT
Hormone use (oral contraceptives, HRT, or exogenous estrogen)
Kline JA, et al. 2004 (derived) · validated 2008 · PERC is only valid in a patient already judged LOW pretest probability (Wells <2). Applying it to a moderate/high-probability patient will miss PE — it was never validated there. Assess SpO₂ on ROOM AIR; a patient already on oxygen cannot be PERC'd.