EBM Consult

PERC Rule in the Evaluation for Pulmonary Embolism in Low-Risk Patients

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 2015

Supporting Guidelines

  • ACEP (American College of Emergency Physicians):

    "In patients with a low pretest probability for suspected pulmonary embolism, consider using the PERC to exclude the diagnosis based on historical and physical examination data alone."

    • Guideline Rating: Level B Recommendation
    • Reference:  Fesmire FM et al. Critical issues in the evaluation and management of adult patients presenting to the emergency department with suspected pulmonary embolism.  Ann Emerg Med 2011;57(6):628-652.  PubMed

Landmark or Original Studies

  • Kline JA et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost 2004;2:1247-55. PubMed

Supporting Studies

  • Singh B et al. Diagnostic accuracy of pulmonary embolism rule-out criteria: a systematic review and meta-analysis. Ann Emerg Med 2012;59:517-520. PubMed

Related Articles & Reviews

  • Michiels JJ et al. Screening for deep vein thrombosis and pulmonary embolism in outpatients with suspected DVT or PE by the sequential use of clinical score: a sensitive quantitative D-dimer test and noninvasive diagnostic tools. Semin Vasc Med 2005;5(4):351-64. PubMed

MESH Terms or Keywords

  • PERC rule, PE, pulmonary embolism, pulmonary thromboembolism