What does a PERC-negative result mean?

If all 8 criteria are absent in a patient with low pretest probability (< 15%), the post-test probability of PE falls below 2% — the accepted miss rate threshold — and no further workup is needed. PERC-negative allows safe discharge or observation without D-dimer or CT.

Can PERC be applied to any patient with suspected PE?

No. PERC is validated only for patients with LOW pretest probability (gestalt < 15%, or Wells ≤ 4). Applying PERC to moderate- or high-probability patients is an error — those patients require D-dimer or imaging regardless.

What does a single positive criterion mean?

Any one positive criterion makes the patient PERC-positive, meaning PE cannot be excluded by PERC alone. The next step is a high-sensitivity D-dimer. If D-dimer is elevated, CT pulmonary angiography follows.

What is the accuracy of the PERC rule?

Prospective validation studies show a sensitivity of approximately 97% and a miss rate under 2% when correctly applied to low-probability patients. Specificity is about 22%, meaning PERC-negative rules out but does not confirm PE.

What counts as "estrogen use" in PERC?

Estrogen use includes oral contraceptive pills, hormone replacement therapy, or any other estrogenic medication currently prescribed. These agents increase thromboembolic risk through effects on coagulation factors.

Does this tool replace clinical judgment?

No. PERC is a decision-support aid. It must be used alongside full clinical assessment, physician experience, vital sign trends, and local institutional protocols. When in doubt, further workup is appropriate.

PERC Rule PE Calculator

Apply all 8 PERC criteria with clinical context to determine whether pulmonary embolism can be safely excluded without D-dimer or imaging.

PERC Criteria

Check each criterion that is present in the patient. PERC applies only when pretest probability is low (< 15%).

Age ≥ 50 years

Thromboembolic risk increases markedly after age 50 due to reduced venous tone, increased comorbidity burden, and age-related changes in coagulation.

Heart rate ≥ 100 bpm

Tachycardia at rest may reflect hypoxia, right heart strain, or sympathetic activation from PE-induced hemodynamic compromise.

SpO₂ < 95% on room air

Pulse oximetry below 95% signals significant ventilation-perfusion mismatch consistent with pulmonary vascular obstruction.

Unilateral leg swelling

Asymmetric lower-extremity edema raises concern for deep vein thrombosis, the most common proximal source of pulmonary emboli.

Hemoptysis

Coughing up blood or blood-tinged sputum may indicate pulmonary infarction caused by arterial occlusion from an embolus.

Recent surgery or trauma (≤ 4 weeks)

Surgery and trauma activate the coagulation cascade and reduce mobility, substantially increasing venous thromboembolism risk in the four weeks following the event.

Prior VTE (DVT or PE)

A personal history of deep vein thrombosis or pulmonary embolism indicates a baseline prothrombotic tendency, making recurrent VTE significantly more likely.

Exogenous estrogen use

Oral contraceptives, hormone replacement therapy, and other estrogenic medications raise thromboembolic risk by altering coagulation factor levels and venous wall compliance.

Result

—

Criteria Present (0 – 8)

—

Criterion	Present

For clinical decision support only. Always integrate with full clinical assessment, vital trends, and institutional protocols.

Summary

The PERC (Pulmonary Embolism Rule-out Criteria) Rule is a validated 8-item clinical decision tool that allows clinicians to exclude pulmonary embolism without further testing in patients with low pretest probability (gestalt below 15%). Developed by Kline et al. and validated across multiple prospective studies, PERC-negative status (all 8 criteria absent) carries a PE miss rate under 2%. This detailed calculator explains each criterion's clinical basis and guides the next diagnostic step.

How it works

Confirm the patient has a low clinical pretest probability of PE — gestalt estimate below 15% or Wells score ≤ 4.
Review each of the 8 PERC criteria and check any that apply to the patient.
If all 8 criteria are absent (PERC-negative), PE is excluded without D-dimer or CT pulmonary angiography.
If any criterion is present (PERC-positive), proceed with high-sensitivity D-dimer or CT pulmonary angiography.
Read the per-criterion rationale to understand why each finding matters for thromboembolic risk.
Document the PERC result alongside pretest probability in clinical notes.

Use cases

Emergency department evaluation of chest pain or dyspnea with low clinical PE suspicion.
Avoiding unnecessary D-dimer tests and radiation exposure from CT pulmonary angiography.
Rapid bedside risk stratification before ordering laboratory or imaging studies.
Teaching the clinical basis of each PERC criterion to students and residents.
Documentation of evidence-based PE workup decisions in low-risk patients.
Quality assurance review of appropriate PERC application in the ED.

Frequently Asked Questions

Last updated: 2026-06-18 · Reviewed by Nham Vu