PE workup · Clinical score
The PERC rule is an eight-criterion bedside decision tool designed to rule out pulmonary embolism without further testing. It is applied in the emergency department only after the clinician has already decided the patient is clinically stable and low enough risk that PE is on the differential but does not need to be pursued aggressively. The band breakdown below summarises the two published outcomes, and the tool beneath it applies the eight criteria live as you tick them.
PERC works by checking for eight binary red flags — age 50 or older, heart rate 100 bpm or greater, SpO₂ below 95% on room air, unilateral leg swelling, hemoptysis, recent surgery or trauma within four weeks, prior venous thromboembolism, and oral hormone use. Clinically stable adults in whom every one of those eight criteria is negative can have further PE workup stopped without a D-dimer, because in that subset the residual probability of PE is lower than the false-positive rate of the D-dimer test itself.
PERC is not a screening tool for the whole department — it is only meant to be applied once the clinician has already decided the patient is haemodynamically stable and a candidate for outpatient workup. Pregnant patients, anticoagulated patients, and those with clear alternative explanations should be considered separately; the rule is a shortcut that has been validated in adult ED populations with low pre-test probability, not as a universal screen.
Outcome by PERC rule status. PERC is a binary rule-out: either all eight criteria are absent or at least one is present. The numbers below are population-level guidance; use them as a decision signal, not an absolute threshold.
PERC negative
Pre-test probability of PE is low enough that the workup can stop. No D-dimer or imaging needed; discharge from the PE pathway is appropriate if no other cause requires it.
PERC positive
PERC does not rule out PE on this patient. Continue through the workup pathway: D-dimer, PERC-adjusted D-dimer, or move to imaging per local protocol.
Open the calculator
Tick the eight PERC criteria. The rule-out decision updates live as you check or uncheck each box, and you can copy or print a clean clinical summary for the chart.
Informational only. Not a substitute for clinical judgement. Not a patient record — PERC results are not persisted; a refresh clears the result. PERC applies only when the clinician is already considering PE and the patient is haemodynamically stable — it is not a screening tool. Always follow your institution’s PE pathway.