Emergency Medicine

PERC Rule

Rules out PE in low-risk patients when all criteria are absent.

Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.

When to use

Use ONLY in patients already judged low pre-test probability for PE. If all 8 criteria are absent (score 0), PE can be excluded without D-dimer.

Why use

It safely avoids unnecessary D-dimer testing in genuinely low-risk patients.

Critical actions

PERC only applies when clinical gestalt is already low risk. It does not apply to moderate/high pre-test probability.

Evidence & references

Kline JA et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected PE. J Thromb Haemost. 2004.

About the creator

Kline JA et al.

Related calculators

Need a calculator we don't have — or a custom tool?

We build evidence-led clinical calculators, dashboards and reference tools for teams.

Request a Custom Tool ☎ +44 7448 439750