Cardiovascular & clot risk

PERC rule

Pulmonary embolism rule-out criteria for a clinician-selected very-low-risk adult.

Intended population: Stable adult emergency patients already judged to have low PE probability (gestalt <15%); not pregnancy/postpartum or therapeutic anticoagulation.

Apply only after clinical assessment identifies low pretest probability. Do not use PERC to lower an intermediate/high pretest probability.
Not validated in people with COVID-19. A positive item means PERC cannot exclude PE; it does not diagnose PE.

Adult with clinician-estimated PE probability <15%, stable, nonpregnant/nonpostpartum, not therapeutically anticoagulated

Age (years)

Heart rate (beats/min)

Room-air oxygen saturation (%)

Unilateral leg swelling

Hemoptysis

Surgery or trauma requiring hospitalization within the past 4 weeks

Previous DVT or PE

Exogenous estrogen use

Sources and scoring references

Kline et al.: original PERC derivation ↗NICE NG158: venous thromboembolic disease ↗

Implementation references reviewed October 28, 2026. Verify applicability and unusual or treatment-changing results against the linked references and local guidance.