PERC rule

The pulmonary embolism rule-out criteria (PERC) may be utilized to negate the need for further pulmonary embolism (PE) workup in patients who are deemed low risk for PE but in whom the diagnosis is being considered .


  • age <50
  • pulse <100 bpm
  • oxygen saturation >95% on room air
  • absence of unilateral leg swelling
  • absence of hemoptysis
  • no recent trauma or surgery
  • no prior history of venous thromboembolism
  • no exogenous estrogen use


If the patient is deemed low risk and meet all of the criteria then there is no need for further PE workup.

If the patient is deemed low risk but is positive for any of the above criteria, a d-dimer should be considered.

If a d-dimer is positive, further investigation such as CTPA or V/Q scan may be indicated.

A meta-analysis of 13,885 patients with 1391 pulmonary embolism diagnoses found that the PERC rule was highly sensitive (0.97, 95% CI 0.96 - 0.98) but poorly specific (0.22, 95% CI 0.22 - 0.24)  in patients with low pretest probability.