PERC Rule

The "Zero" Score Search: Only for very low pretest probability (< 15% gestalt). If ALL 8 answers are "Yes," PE is safely ruled out without a D-dimer.

Age < 50 years

Heart Rate < 100 bpm

SpO2 ≥ 95% on room air

No unilateral leg swelling

No hemoptysis

No recent surgery or trauma (< 4 weeks)

No prior PE or DVT

No oral hormone use

Guidelines & Evidence

Verified

Last Review: 2026-07-17

When to Use

Ruling out Pulmonary Embolism (PE) in patients with a very low clinical pretest probability.

Reducing unnecessary D-dimer testing and subsequent imaging in the emergency department.

Applying to patients where the clinician's gestalt of PE is < 15%.

The 'All or Nothing' Rule

If ANY of the 8 criteria are positive, the PERC rule is considered "positive" and a D-dimer should be performed. Only if ALL 8 are negative can PE be safely ruled out.

How it Works

The 8 Rule-out Factors

Age < 50 years.

Heart Rate < 100 bpm.

Oxyhemoglobin Saturation (SpO₂) ≥ 95%.

No unilateral leg swelling.

No hemoptysis.

No recent surgery or trauma (within previous 4 weeks).

No prior PE or DVT.

No oral hormone use (contraception, HRT, or glucocorticoids).

Interpretation

Condition	Result	Clinical Action
All 8 Criteria Met	PERC Negative	PE Ruled Out (Likelihood < 1%)
Any Criterion Not Met	PERC Positive	Indication for D-dimer

Last Comprehensive Review: 2026-07-17

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PERC Rule

When to Use

When to Use

The 'All or Nothing' Rule

How it Works

The 8 Rule-out Factors

Interpretation

Clinical Pearls

Avoiding the D-dimer Trap

Hormone Scope

The Evidence

Primary Strategy

Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism.

Effect of the Pulmonary Embolism Rule-out Criteria on subsequent thromboembolic events.

Origins & History

History

Recent Journal Updates

PERC Rule

When to Use

When to Use

The 'All or Nothing' Rule

How it Works

The 8 Rule-out Factors

Interpretation

Clinical Pearls

Avoiding the D-dimer Trap

Hormone Scope

The Evidence

Primary Strategy

Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism.

Effect of the Pulmonary Embolism Rule-out Criteria on subsequent thromboembolic events.

Origins & History

History

Recent Journal Updates