GuiDeCode
Calcs › ♥ Cardiovascular / Vascular

PERC Rule

Pulmonary Embolism Rule-out Criteria — excludes PE without testing

Calculator

Loading calculator…

Why use it

Eliminates need for D-dimer in very low-risk patients. Prevents the false-positive cascade (elevated D-dimer → unnecessary CTPA). Validated with < 2% miss rate when properly applied.

About

The PERC rule identifies very low-risk patients in whom PE can be excluded without D-dimer testing or imaging. If ALL 8 criteria are absent in a patient with low clinical suspicion (Wells ≤ 4 or gestalt < 15%), PE can be safely excluded. PERC reduces unnecessary D-dimer testing and its associated false-positive cascade.

When to use

  • Low clinical suspicion for PE (Wells ≤ 4 or physician gestalt < 15%)
  • Before ordering D-dimer in low-risk chest pain or dyspnea patients

Formula

ALL must be absent to rule out PE: 1. Age < 50 2. HR < 100 3. SpO₂ ≥ 95% on room air 4. No unilateral leg swelling 5. No hemoptysis 6. No recent surgery/trauma (≤ 4 weeks) 7. No prior PE/DVT 8. No estrogen use (OCP, HRT)

Pearls & pitfalls

  • PERC is ONLY for LOW pre-test probability patients. Never apply to moderate/high risk.
  • ALL 8 criteria must be absent to rule out PE. Even one positive criterion = proceed to D-dimer.
  • PERC is meant to AVOID testing, not to diagnose. It is a rule-out tool only.
  • Do NOT apply PERC to hospitalized patients or those with strong clinical suspicion.
  • The concept: if PE testing would cause more harm than benefit in very low-risk patients, skip it.
  • Validated miss rate < 2% (below the test threshold).

Next steps

All criteria negative (PERC negative): PE excluded, no further testing needed. Any criterion positive: PERC positive — proceed with D-dimer testing. PERC should only be applied when pre-test probability is LOW.

Evidence

Derived by Kline et al. (J Thromb Haemost, 2004). Validated in the PROPER trial (JAMA 2018, non-inferiority) in French EDs. Miss rate ~1% when applied to low pre-test probability patients.

References

  1. Kline JA et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247-1255. — link
  2. Freund Y et al. Effect of the Pulmonary Embolism Rule-Out Criteria on subsequent thromboembolic events among low-risk emergency department patients (PROPER). JAMA. 2018;319(6):559-566. — link