PERC Rule for Pulmonary Embolism Calculator

Pulmonary Embolism Rule-out Criteria (PERC) — 8 criteria to exclude PE in low-risk patients.

For educational and clinical reference. Not a substitute for medical judgment. See the medical disclaimer.
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References

  1. Kline JA, Mitchell AM, Kabrhel C, 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.

What is PERC Rule for Pulmonary Embolism?

The PERC (Pulmonary Embolism Rule-out Criteria) is an eight-item clinical decision rule that safely excludes pulmonary embolism without D-dimer testing or imaging in patients judged to have a low pre-test probability. Derived by Kline et al. in 2004 and prospectively validated in 2008, the criteria are: age <50, heart rate <100, oxygen saturation ≥95% on room air, no unilateral leg swelling, no hemoptysis, no recent trauma or surgery within 4 weeks, no prior DVT/PE, and no estrogen use. If a patient has a low gestalt probability and meets all eight criteria, the post-test probability of PE is <2%, and no further workup is warranted.

How to use

  1. Confirm the pretest probability of PE is low before applying PERC.
  2. Select any of the 8 criteria that are present.
  3. If all 8 are absent (PERC negative), PE can be excluded without further testing.

Frequently asked questions

What is the PERC rule?

The Pulmonary Embolism Rule-out Criteria: 8 bedside criteria that, when all negative in a patient with low pretest probability, allow PE to be excluded without D-dimer testing.

When can PERC be applied?

Only when the clinical gestalt pretest probability for PE is already low (< 15%). PERC should not be used in moderate- or high-risk patients.

What is the missed-PE rate if PERC negative?

In appropriately low-risk patients, a negative PERC carries a < 2% probability of PE — below the testing threshold.

Does any positive criterion mean the patient has a PE?

No. A positive PERC simply means PE cannot be excluded by the rule alone — continue the standard work-up (D-dimer, then imaging if indicated).

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