Apply the eight PERC criteria to see whether pulmonary embolism can be ruled out in a low-risk patient without further testing.
Result
How to use this tool
Confirm the patient is already judged low risk.
Answer all eight criteria.
Read whether PERC is negative or positive.
Follow local testing pathways for any positive result.
Formula & worked example
A low-risk patient with none of the eight PERC criteria positive is PERC negative, so embolism can be ruled out without further testing.
Limitations — read this before you rely on it
Rule-out aid for low-probability patients only. It must not be used to rule out embolism in moderate or high probability patients. This tool is for education only and is not medical advice. Talk to a clinician about any result that worries you, and never change treatment because of a calculator result.
Frequently asked questions
Age 50 or older, heart rate 100 or more, saturation below 95%, unilateral leg swelling, haemoptysis, recent surgery or trauma, prior clot, and hormone use.
Only patients already judged low risk for pulmonary embolism by clinical assessment.
PERC is positive and cannot rule out embolism — D-dimer or imaging follows local pathways.
No. It only rules out, and only in low-risk patients.
Severe breathlessness, chest pain or collapse needs emergency assessment regardless of any score.