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PERC Rule for PE

Emergency MedicinePulmonology

Medical context

Apply the PERC rule to help rule out pulmonary embolism in low-risk patients.

Emergency clinicians use this at triage, resuscitation, and disposition to standardize risk communication across shifts.

This page explains the PERC formula, how to interpret the output, known limitations, and peer-reviewed references so you can verify results against primary sources and local protocols.

It is grouped under Emergency Medicine because trauma, triage, and acute risk scores used in the ed.

How to use this calculator

  1. Enter the values requested by the PERC calculator using the units shown beside each field.
  2. Review the calculated result and read the interpretation section before acting on the output.
  3. Check limitations and references if the result will change management, dosing, or disposition.
  4. Use the related calculators section when you need supporting values (for example electrolytes, weight, or complementary risk scores).

Calculator

Result

Negative

PERC negative — PE unlikely if pretest probability is low

0 criterion(s) present. Only apply when clinical suspicion is already low.

Educational use only. Confirm results with clinical judgment, primary sources, and local protocols. Not a substitute for professional medical advice. Full disclaimer.

Formula

Eight criteria; PERC negative only if all are absent and pretest probability is already low.

Interpretation

PERC negative may avoid D-dimer/imaging in truly low-risk patients; any positive criterion means PERC cannot rule out PE.

Limitations

Do not apply when suspicion is moderate/high. Gestalt of low risk is required.

Frequently asked questions

Can PERC replace Wells?
No — PERC is a rule-out tool after you already judge risk to be low.
Is the PERC result enough to make a treatment decision?
No. Calculators support medical decision-making but do not replace examination, shared decision-making, institutional protocols, or consultant input when stakes are high.
Does Calcmedical store the values I type in?
Inputs are processed in your browser for this session. We do not ask for patient names or medical record numbers. See our privacy policy for hosting and analytics details.

References

  • Kline JA et al. PERC rule