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PERC Rule

Rules out pulmonary embolism without further testing in patients already judged low pretest probability — only valid when applied to that population.

For healthcare professionals.These calculate a score or a measurement from values you enter. They do not diagnose, and they are no substitute for clinical judgement. If you are a patient, discuss any result with your own doctor rather than acting on it.

Age ≥ 50 years

Heart rate ≥ 100 bpm

SpO₂ < 95% on room air

Hemoptysis

Estrogen use (OCP, HRT, or estrogen-containing gender-affirming therapy)

Prior DVT or PE

Unilateral leg swelling

Surgery or trauma requiring hospitalization within the past 4 weeks

Result

PERC Negative

Negative

All 8 criteria negative — in a patient already judged low pretest probability, PE can be excluded without further testing (associated miss rate <2%).

Do not use when

Only validated for use in patients the clinician has already judged low pretest probability (e.g. gestalt <15%, or low-risk by Wells) — do not apply PERC to moderate/high pretest probability patients.

Source

Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247-1255.

Shown for reference and checked against the source above. Confirm against current guidance before acting on it, and use your own clinical judgement.

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