PERC Rule (PE rule-out)
PERC rule (Kline 2004): eight rule-out criteria (age >= 50, HR >= 100, SaO2 < 95%, hemoptysis, estrogen, prior VTE, recent surgery/trauma, unilateral leg swelling).
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Age >= 50
- Yes
Result: PERC 1 positive feature (age >= 50): rule-out does NOT apply.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- 0 features positive
- PERC negative. In patients with low pretest probability, PE can be excluded without further testing per source.
- >=1 feature positive
- PERC positive. Rule-out does not apply; further evaluation per source.
What you enter
- Age >= 50
- HR >= 100
- SaO2 < 95%
- Hemoptysis
- Estrogen use
- Prior VTE
- Recent surgery or trauma
- Unilateral leg swelling
What this is
Check the eight-item Pulmonary Embolism Rule-out Criteria (Kline 2004): age <50, HR <100, SpO2 >=95% on room air, no hemoptysis, no exogenous estrogen, no prior DVT/PE, no recent surgery or trauma, and no unilateral leg swelling. If every criterion is satisfied in a patient who is already low pretest probability, PE can be ruled out without further workup.
When to use it
Apply PERC only after clinical gestalt or Wells has already established a low pretest probability for PE. PERC is a rule-out aid for that specific population - it is not a screening test, and a single failed criterion does not diagnose PE; it only means PERC cannot be used and the workup continues with D-dimer or imaging.
How this is calculated
Kline JA, et al. PERC rule. J Thromb Haemost. 2004;2(8):1247-1255. Use only if clinical pretest probability is low. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.
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