Clinical Overview

The Pulmonary Embolism Rule-out Criteria is an eight-item decision rule designed to identify a subgroup of adults with suspected pulmonary embolism whose risk is already very low and in whom further testing may cause more harm than benefit. It is applied only after clinical assessment establishes a sufficiently low pretest probability; the checklist itself does not create that low-risk status.

Every item must be negative for a PERC-negative result. If any item is positive, PERC has not excluded pulmonary embolism and the clinician should follow the applicable probability-adjusted D-dimer or imaging pathway. Stabilization, bedside assessment, and urgent diagnostic planning take priority in hemodynamic compromise.

When to Use

• Hemodynamically stable adults with suspected PE and an independently assessed very low pretest probability
• Avoidance of unnecessary D-dimer testing only within a validated diagnostic pathway

Limitations & Safety

Performance depends on disease prevalence and the clinician’s accurate prior assessment. Pregnancy, postpartum physiology, higher-prevalence settings, inpatient care, and anticoagulation may fall outside common validation populations. Borderline measurements should be verified rather than rounded into a negative result.

A PERC-negative result does not explain symptoms or rule out other dangerous diagnoses. Reassess if symptoms persist, vital signs change, or the clinical picture is discordant. Follow current local PE guidance, especially for age-adjusted or probability-adjusted D-dimer strategies.

• Do not apply when pretest probability is not very low
• Not validated for unstable patients, pregnancy, or populations with substantially higher PE prevalence

Formula / Scoring Criteria

PERC negative requires all eight: age <50, pulse <100, oxygen saturation ≥95%, no unilateral leg swelling, no hemoptysis, no recent surgery/trauma, no prior VTE, and no exogenous estrogen

Interpretation

• 0 positive criteria — PERC negative: Very low residual PE risk only when prior probability was very low. No D-dimer may be needed within a validated pathway.
• ≥1 positive criterion — PERC positive: PE is not excluded. Continue with D-dimer or imaging based on clinical probability.

Evidence & References

1. Kline JA, et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected PE.
2. Freund Y, et al. Effect of the PERC rule on subsequent thromboembolic events (PROPER trial).

Clinical FAQs

Can PERC be applied before assessing clinical probability?

No. It is intended only after an experienced clinician judges PE probability to be very low.

Does PERC positivity diagnose PE?

No. One positive item means only that PERC cannot rule PE out.

Can PERC be used in pregnancy?

Standard PERC is not sufficiently validated as a stand-alone pregnancy rule; use a pregnancy-appropriate pathway.