title: The number of patients simultaneously present at the emergency department as an indicator of unsafe waiting times: a receiver operated curve-based evaluation.
abstract: BACKGROUND
  Emergency department (ED) crowding and prolonged waiting times have been associated with adverse consequences towards quality and patient safety.
  
  
  OBJECTIVE
  This study investigates whether the number of patients simultaneously present at the ED might be an indicator of unsafe waiting and at what threshold hospital-wide measures to improve patient outflow could be justified.
  
  
  METHODS
  Data were retrospectively collected during a 1-year period; all ED patients aged ≥16 years, and triaged as ESI-1 or ESI-2 were eligible for inclusion. The number of patients simultaneously present was used as occupancy rate. Waiting time was considered unsafe if it was longer than 10 min for ESI-1 patients, or longer than 30 min for ESI-2 patients. Differences in waiting time and occupancy between patients with safe and unsafe waiting times were analysed using the Mann-Whitney U test. The ability of the occupancy rate to discriminate unsafe waiting times was analysed using a receiver operating characteristic curve.
  
  
  RESULTS
  The overall median waiting time was 5 min (IQR=4-8) for ESI-1, and 12 min (IQR=6-24) for ESI-2 patients. Unsafe waiting times occurred in 16.0% of ESI-1 patients (median waiting time=17 min, IQR=13-23), and in 18.9% of ESI-2 patients (median waiting time=48 min, IQR=37-68). The occupancy rate was a weak indicator for unsafe waiting times in ESI-1 patients (AUC=0.625, 95%CI 0.537-0.713) but a fair indicator for unsafe waiting times in ESI-2 patients (AUC=0.740, 95%CI 0.727-0.753) for which the threshold to predict unsafe waiting times with 90% sensitivity was 51 patients.
  
  
  CONCLUSIONS
  The number of patients simultaneously present is a moderate indicator of unsafe waiting times. Future initiatives to improve safe waiting times should not focus solely on occupancy, and expand their focus towards other factors affecting waiting time.
authors: Patient Safety Research Group, Faculty of Business Economics, Hasselt University, Hasselt, Belgium. Electronic address: jochen.bergs@uhasselt.be.
authors: Jochen
authors: J
authors: Bergs
authors: Department of Emergency Medicine, Leuven University Hospitals, Leuven, Belgium.
authors: Sandra
authors: S
authors: Verelst
authors: Department of Emergency Medicine, Leuven University Hospitals, Leuven, Belgium.
authors: Jean-Bernard
authors: JB
authors: Gillet
authors: Department of Emergency Medicine, Leuven University Hospitals, Leuven, Belgium.
authors: Peter
authors: P
authors: Deboutte
authors: Department of Business Intelligence, Leuven University Hospitals, Leuven, Belgium.
authors: Cindy
authors: C
authors: Vandoren
authors: Patient Safety Research Group, Faculty of Business Economics, Hasselt University, Hasselt, Belgium; Department of Public Health and Health Economics, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
authors: Dominique
authors: D
authors: Vandijck
mesh_terms: D001509:Bed Occupancy / Q000592:standards*; D001530:Belgium; D004636:Emergency Service, Hospital / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D061214:Patient Safety; D012189:Retrospective Studies; D013997:Time Factors; D014218:Triage / Q000592:standards*
keywords: Appointments and schedules/statistics and numerical data; Crowding; Emergency nursing; Emergency service, hospital; Patient safety; ROC curve; Triage