title: PERC rule to exclude the diagnosis of pulmonary embolism in emergency low-risk patients: study protocol for the PROPER randomized controlled study.
abstract: BACKGROUND
  The diagnosis of Pulmonary Embolism (PE) in the emergency department (ED) is crucial. As emergency physicians fear missing this potential life-threatening condition, PE tends to be over-investigated, exposing patients to unnecessary risks and uncertain benefit in terms of outcome. The Pulmonary Embolism Rule-out Criteria (PERC) is an eight-item block of clinical criteria that can identify patients who can safely be discharged from the ED without further investigation for PE. The endorsement of this rule could markedly reduce the number of irradiative imaging studies, ED length of stay, and rate of adverse events resulting from both diagnostic and therapeutic interventions. Several retrospective and prospective studies have shown the safety and benefits of the PERC rule for PE diagnosis in low-risk patients, but the validity of this rule is still controversial. We hypothesize that in European patients with a low gestalt clinical probability and who are PERC-negative, PE can be safely ruled out and the patient discharged without further testing.
  
  
  METHODS
  This is a controlled, cluster randomized trial, in 15 centers in France. Each center will be randomized for the sequence of intervention periods: a 6-month intervention period (PERC-based strategy) followed by a 6-month control period (usual care), or in reverse order, with 2 months of "wash-out" between the 2 periods. Adult patients presenting to the ED with a suspicion of PE and a low pre test probability estimated by clinical gestalt will be eligible. The primary outcome is the percentage of failure resulting from the diagnostic strategy, defined as diagnosed venous thromboembolic events at 3-month follow-up, among patients for whom PE has been initially ruled out.
  
  
  CONCLUSIONS
  The PERC rule has the potential to decrease the number of irradiative imaging studies in the ED, and is reported to be safe. However, no randomized study has ever validated the safety of PERC. Furthermore, some studies have challenged the safety of a PERC-based strategy to rule-out PE, especially in Europe where the prevalence of PE diagnosed in the ED is high. The PROPER study should provide high-quality evidence to settle this issue. If it confirms the safety of the PERC rule, physicians will be able to reduce the number of investigations, associated subsequent adverse events, costs, and ED length of stay for patients with a low clinical probability of PE.
  
  
  BACKGROUND
  NCT02375919 .
authors.affiliation: Paris Sorbonne Université, UPMC univ-Paris 6, UMRS INSERM 1166, IHU ICAN, Paris, France. yonathanfreund@gmail.com.|Emergency Department, Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France. yonathanfreund@gmail.com.
authors.forename: Yonathan
authors.initials: Y
authors.lastname: Freund
authors.affiliation: Plateforme de recherche clinique de l'est parisien (URCEST-CRCEST), Hôpital St Antoine, APHP, Paris, France. Alexandra.rousseau@aphp.fr.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rousseau
authors.affiliation: Plateforme de recherche clinique de l'est parisien (URCEST-CRCEST), Hôpital St Antoine, APHP, Paris, France. France.guyot@aphp.fr.
authors.forename: France
authors.initials: F
authors.lastname: Guyot-Rousseau
authors.affiliation: Emergency Department, Princess Grace Hospital, Monte Carlo, Monaco. yann-erick.claessens@chpg.mc.
authors.forename: Yann-Erick
authors.initials: YE
authors.lastname: Claessens
authors.affiliation: Emergency Department, Lausanne University Hospital, Lausanne, Switzerland. Olivier.Hugli@chuv.ch.
authors.forename: Olivier
authors.initials: O
authors.lastname: Hugli
authors.affiliation: Pneumology and Intensive Care Unit, Hôpital Européen Georges Pompidou, APHP, Université Paris Descartes, Sorbonne Paris Cite, Paris, France. Olivier.sanchez@aphp.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Sanchez
authors.affiliation: Paris Sorbonne Université, UPMC univ-Paris 6, UMRS INSERM 1166, IHU ICAN, Paris, France. tabassome.simon@aphp.fr.|Plateforme de recherche clinique de l'est parisien (URCEST-CRCEST), Hôpital St Antoine, APHP, Paris, France. tabassome.simon@aphp.fr.
authors.forename: Tabassome
authors.initials: T
authors.lastname: Simon
authors.affiliation: Paris Sorbonne Université, UPMC univ-Paris 6, UMRS INSERM 1166, IHU ICAN, Paris, France. bruno.riou@aphp.fr.|Emergency Department, Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France. bruno.riou@aphp.fr.
authors.forename: Bruno
authors.initials: B
authors.lastname: Riou
mesh_terms: D002985:Clinical Protocols; D003661:Decision Support Techniques; D003951:Diagnostic Errors / Q000517:prevention & control; D004632:Emergency Medical Services; D005602:France; D006801:Humans; D011237:Predictive Value of Tests; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000209:etiology; D012107:Research Design; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D019564:Unnecessary Procedures; D054556:Venous Thromboembolism / Q000175:diagnosis* / Q000209:etiology; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000209:etiology