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PERC rule

Pulmonary Embolism Rule-out Criteria — skip D-dimer when gestalt probability is already low

Sources last checked: 2026-10-13

PERC rule

Pulmonary Embolism Rule-out Criteria — skip D-dimer when gestalt probability is already low

PERC negative

No criterion present. Only if gestalt pre-test probability is low (< 15 %): PE can be considered ruled out without D-dimer.

Apply only when the clinician's unstructured estimate of PE probability is already low (< 15 %). In higher-prevalence European emergency populations the miss rate is higher; ESC 2019 and AWMF 2023 both note limited generalisability.

Source: Kline JA 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.Open

Interpretation

PERC negativeNo criterion present. Only if gestalt pre-test probability is low (< 15 %): PE can be considered ruled out without D-dimer.
PERC positiveAt least one criterion present: PERC cannot rule out PE, and the validated pathways (Wells / Geneva + D-dimer) apply.

What is the PERC rule?

The Pulmonary Embolism Rule-out Criteria are eight bedside items derived by Kline and colleagues from 3,148 US emergency patients (J Thromb Haemost 2004). In a patient whom the clinician already judges to be at low risk, the absence of all eight lowers the probability of PE below the threshold at which a D-dimer is worth doing. The French PROPER trial (JAMA 2018) supported its safety in low-prevalence emergency departments.

When to use it

  • Emergency patients with chest pain or dyspnoea in whom PE is a consideration but gestalt probability is low (< 15 %).
  • To avoid an unnecessary D-dimer — and the downstream CTPA that a false-positive brings.
  • In settings with low PE prevalence, similar to the derivation and validation cohorts.

When not to use it

  • Intermediate or high clinical probability — PERC does not apply; the ESC 2019 pathways use Wells or Geneva with D-dimer, or imaging.
  • Inpatients, pregnant patients or populations with high PE prevalence.
  • Where pulse oximetry is unreliable or the patient is already on oxygen.

Clinical pearls and limitations

  • Apply only when the clinician's unstructured estimate of PE probability is already low (< 15 %). In higher-prevalence European emergency populations the miss rate is higher; ESC 2019 and AWMF 2023 both note limited generalisability.
  • PERC is binary: a single positive criterion means PERC cannot be used to rule out PE — it does not mean PE is likely.
  • Saturation must be measured on room air; the criterion is SaO₂ > 94 %.
  • ESC 2019 and AWMF 2023 note that the low PE prevalence in validation studies limits transfer to European emergency departments.
  • Gestalt comes first: PERC is only valid after the clinician has independently judged the risk to be low.

Frequently asked questions

What are the 8 PERC criteria?

Age < 50, heart rate < 100/min, SaO₂ > 94 % on room air, no haemoptysis, no oestrogen use, no prior DVT/PE, no unilateral leg swelling, and no surgery or trauma in the past 4 weeks. All eight must be met.

Is PERC used in Europe?

It is discussed in the ESC 2019 and German AWMF 2023 guidelines with a caveat about limited generalisability. The French PROPER trial supported it in low-risk emergency patients.

PERC negative — do I need a D-dimer?

If gestalt probability is low and all criteria are met, the original authors consider further testing unnecessary. If gestalt is not low, PERC does not apply.

Evidence and guidelines

  1. Primary source: Kline JA 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.
  2. Kline JA et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost 2008;6(5):772-780.
  3. Freund Y et al. Effect of the PERC rule on subsequent thromboembolic events among low-risk ED patients (PROPER). JAMA 2018;319(6):559-566.
  4. ESC 2019 acute PE guideline (PERC discussed; generalisability limited by low PE prevalence in validation cohorts).
  5. AWMF S2k 065-002 (2023), section 3.2.1 (PERC-Kriterien, eingeschränkte Übertragbarkeit).

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