Differentiating Low-Risk and No-Risk PE Patients: The PERC Score
Christopher R. Carpenter, MD, MSC, FAAEM; Samuel M. Keim, MD, MS; Rawle A. Seupaul, MD; Jesse M. Pines, MD, MBA, MSCE; The Best Evidence in Emergency Medicine Investigator Group. Published: 05/14/2009
Background: Pulmonary embolism (PE) remains one of the most challenging diagnoses in emergency medicine. The Pulmonary Embolism Rule-out Criteria (PERC) score, a decision aid to reliably distinguish low-risk from very low-risk PE patients, has been derived and validated.
Clinical Question: Can a subset of patients with sufficiently low risk for PE be identified who require no diagnostic testing?
Evidence Review: The PERC score derivation and validation trials were located using PubMed and Web of Science. A critical appraisal of this research is presented.
Results: One single-center and another multi-center validation trial both confirmed that the eight-item PERC score identified a very low-risk subset of patients in whom PE was clinically contemplated with a negative likelihood ratio 0.17 (95% confidence interval 0.11-0.25) in the larger trial. If applied, the rule would have identified 20% of potential PE patients as very low risk.
Conclusion: The PERC score provides clinicians with an easily remembered, validated clinical decision rule that allows physicians to forego diagnostic testing for pulmonary embolus in a very low-risk population.
Age below 50 years
Pulse below 100 beats/min
Pulse ox above 94%
No unilateral leg swelling
No recent surgery
No prior DVT or PE
No oral hormone use
PERC = pulmonary embolism rule-out criteria; min = minute; pulse ox = pulse oximeter reading; DVT = deep venous thrombosis; PE = pulmonary embolism.