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PERC rule (pulmonary embolism rule-out criteria)

Also called PERC, Kline rule

Eight bedside criteria that rule out PE without a D-dimer when clinical suspicion is already low.

PERC

Negative (0 of 8)

All eight criteria met. With a low gestalt pretest probability (<15%), PE can be ruled out without D-dimer: the false-negative rate was 1.0% in the 8,138-patient US multicentre study.

Formula and scoring

PERC negative only when every item is absent: age <50, HR <100, SaO₂ ≥95%, no haemoptysis, no oestrogen use, no surgery/trauma in 4 weeks, no prior VTE, no unilateral leg swelling.

Exam and ward pearls

  • PERC is applied only after the clinician already judges PE unlikely (gestalt <15%); it is not a screening tool for everyone with dyspnoea.

When not to rely on it

  • Derived and validated in US emergency departments; the safety data apply only when combined with a low gestalt pretest probability (<15%).

Source

  1. Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247-55. doi:10.1111/j.1538-7836.2004.00790.x · PMID 15304025
  2. Kline JA, Courtney DM, Kabrhel C, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost. 2008;6(5):772-80. doi:10.1111/j.1538-7836.2008.02944.x · PMID 18318689

Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.

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