Summary:
The PERC (Pulmonary Embolism Rule-out Criteria) rule can be used in the initial evaluation for pulmonary embolism (PE) in low-risk patients to exclude the diagnosis of PE based on historical and physical examination data alone.  A patient's low-risk risk status can be determined by either clinician judgement or by using Wells Criteria. If a patient fails to meet any of the below criteria then a D-dimer can be done to aid in the decision of whether or not the patient should get a CT angiography of the chest to rule out the presence of a PE.

Interpretation:
If the patient you are evaluating is considered to be low-risk by either clinician judgement or by using Wells Criteria and then meets all of the PERC criteria, then there is a good chance the patient does not have a pulmonary embolism (PE) and does not need additional testing, but if they fail to meet even one of the criteria, then additional testing or evaluation should be considered. This rule is a screening tool with high sensitivity, but low specificity. In other words, a patient meeting all of the PERC criteria has a very low likelihood of having a PE, but a person failing to meet all of the criteria does not necessarily have a PE.

The PERC criteria are used to help the clinician do a bedside assessment to determine if a patient is at "very low risk" for pulmonary embolism and does not warrant additional diagnostic evaluation, including a D-dimer.  The PERC criteria includes:
    - Age < 50 yrs
    - Pulse < 100 bpm
    - SaO2 > 94%
    - No unilateral swelling
    - No hemoptysis
    - No recent trauma or surgery
    - No prior PE or DVT
    - No hormone use  

Additional Clinical Considerations:

• The PERC rule reduced the pre-test probability below the test threshold for D-dimer evaluation in validated populations, but is limited by its low specificity.
• While immobility was significantly associated with risk for venous thromboembolism, it was not included in the PERC rule due to low interobserver agreement within the study. 
• Application of the PERC rule to low-risk patients resulted in a sensitivity of 96% and specificity of 27%.  
  • Note: Low-risk patients (clinical suspicion for PE and met the PERC rule criteria) had a prevalence of PE of 1.4% (95% CI, 0.5 - 3.0%). 
• Application of the PERC rule to patients at "very-low risk" resulted in a sensitivity of 100% and specificity of 15%.  
  • Note: Very low-risk patients (presenting with chief complaint of dyspnea or some other breathing complaint and where PE is not suspected, but met the PERC rule criteria) have a prevalence of PE of 0% (95% CI, 0 - 6.2%).

Editors: 

• Anthony J. Busti, MD, PharmD, FNLA, FAHA 
• Dylan Kellogg, MD

Last Reviewed: July 202022