Who can the PERC rule be applied to?

The PERC rule is valid ONLY for patients with LOW pre-test probability of PE — typically defined as a Wells PE score of 0–1 or a physician gestalt of less than 15% pre-test probability. Applying PERC to intermediate- or high-risk patients is inappropriate and unsafe.

What does PERC negative mean?

PERC negative means all 8 criteria are absent. In a low-pretest-probability patient, this reduces the post-test probability of PE to under 2%, the accepted clinical threshold for withholding further testing. No D-dimer or CT-PA is required.

What happens if even one criterion is positive?

A single positive criterion makes the rule PERC positive. You should proceed with D-dimer testing and, if elevated, CT pulmonary angiography per standard workup protocols.

What is the evidence base for the PERC rule?

The PERC rule was derived by Kline et al. (2004) and validated in multiple prospective studies. A 2008 multicenter validation showed a sensitivity of 97.4% and a miss rate under 2% in low-risk patients. It is endorsed by ACEP and widely used in US emergency departments.

Does this tool store any patient data?

No. All logic runs entirely in your browser. No data is transmitted to any server and nothing is stored.

Can the PERC rule replace clinical judgment?

No. The PERC rule is a decision-support aid, not a replacement for full clinical assessment. Always integrate it with the overall clinical picture and consult appropriate specialists when uncertain.

PERC Rule for PE (Simplified)

Check all 8 PERC criteria to determine whether PE can be ruled out without D-dimer testing in low-pretest-probability patients.

PERC Criteria

Answer each criterion based on the patient's current presentation. Rule applies only to low pre-test probability patients.

Result

0 positive

of 8 criteria positive

Awaiting input

Answer the criteria on the left to see the PERC interpretation.

Criteria answered: 0 / 8

Important: Use only after confirming low pre-test probability (Wells PE ≤ 1 or clinical gestalt < 15%). This tool supports, but does not replace, clinical judgment.

Summary

The PERC rule is a validated clinical decision tool used in emergency medicine to rule out pulmonary embolism (PE) without ordering a D-dimer test. It applies only to patients already assessed as low pre-test probability by gestalt or Wells criteria. If ALL 8 criteria are negative (PERC negative), the post-test probability of PE drops below 2% and further workup can be safely withheld. If ANY criterion is positive, the rule is not satisfied and D-dimer or imaging should follow.

How it works

Establish low pre-test probability for PE using clinical gestalt or Wells score before applying PERC.
Answer each of the 8 yes/no criteria based on the patient's current presentation and history.
If all 8 criteria are answered "No," the rule is PERC negative — PE workup can stop here.
If any single criterion is answered "Yes," the rule is PERC positive — proceed with D-dimer or imaging per your institution's protocol.
Document the result alongside the pre-test probability assessment in the clinical note.

Use cases

Rule out PE in low-risk ED patients to avoid unnecessary D-dimer testing.
Reduce radiation exposure by preventing reflex CT pulmonary angiography.
Support clinical documentation for PE workup decisions.
Teach emergency medicine residents the PERC rule-out pathway.
Streamline triage in busy emergency departments.
Identify patients who still need D-dimer despite initially appearing low risk.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu