PERC Rule for PE
Rules out PE without further testing in low pretest probability patients
How to use & interpret
The PERC rule helps avoid D-dimer testing in patients in whom PE is already clinically unlikely. It applies only when your gestalt pre-test probability is low (<15%) — typically 'PE unlikely' by Wells.
If all eight criteria are negative (age <50, HR <100, SpO₂ ≥95%, no haemoptysis, no oestrogen use, no prior DVT/PE, no unilateral leg swelling, no recent surgery/trauma), the risk of PE is low enough that no further testing is needed. A single positive criterion does not diagnose PE — it just means PERC cannot exclude it, so proceed to D-dimer or imaging. Never apply PERC to moderate- or high-probability patients.
Score interpretation
All 8 criteria absent. PE can be excluded without D-dimer.
→ No further workup required for PE in low pretest probability patients
One or more criteria present. Cannot exclude PE by PERC alone.
→ Proceed with D-dimer; if elevated, CTPA
Interpretation bands for the PERC. Apply clinical judgement and local guidance.
Frequently asked questions
Does a positive PERC criterion mean the patient has a PE?
No. It only means PE cannot be ruled out by PERC alone, so you continue the normal pathway (age-adjusted D-dimer or imaging as indicated).
References
- 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):1247–55.
Related
Curated clinical cross-links plus same-class fallbacks.
- HERDOO2 Rule for Discontinuing Anticoagulation in Unprovoked VTE · Venous Thromboembolism
- RIETE Score for Bleeding Risk in VTE · Venous Thromboembolism
- Wells Criteria for PE · Venous Thromboembolism
- Wells Criteria for DVT · Venous Thromboembolism
- Revised Geneva Score for PE · Venous Thromboembolism
- Wells DVT Score · Venous Thromboembolism
- Rivaroxaban (PE Treatment) · Venous Thromboembolism
- Nitric Oxide (Inhaled — iNO) · Selective Pulmonary Vasodilator
- Selexipag · Pulmonary Arterial Hypertension
- Macitentan · Pulmonary Arterial Hypertension
- Sildenafil (Paediatric — PPHN / PAH) · PDE5 Inhibitor (Paediatric Pulmonary Hypertension)
- Sildenafil · PDE5 Inhibitor — Pulmonary Arterial Hypertension
- Difficult Airway Algorithm (DAS) · DAS 2015; Royal College of Anaesthetists
- Major Haemorrhage Protocol · NICE NG24; UK MHP guidelines
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines
Featured in these MRCEM clinical pathways
The PERC is covered in detail — with RCEM/NICE evidence base, indications and pitfalls — in the following exam-focused pathways on our sister siteReviseMRCEM.
MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.