title: Differentiating low-risk and no-risk PE patients: the PERC score.
abstract: 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.
  
  
  OBJECTIVE
  Can a subset of patients with sufficiently low risk for PE be identified who require no diagnostic testing?
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Carpenter
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Keim
authors.forename: Rawle A
authors.initials: RA
authors.lastname: Seupaul
authors.forename: Jesse M
authors.initials: JM
authors.lastname: Pines
mesh_terms: D000328:Adult; D000933:Antifibrinolytic Agents; D003937:Diagnosis, Differential; D004636:Emergency Service, Hospital; D005189:False Positive Reactions; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products; D006801:Humans; D010092:Oximetry; D011655:Pulmonary Embolism / Q000175:diagnosis*; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed
chemical_list: D000933:Antifibrinolytic Agents; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D