title: Setting wait times to achieve targeted left-without-being-seen rates.
abstract: BACKGROUND
  Although several studies have demonstrated that wait time is a key factor that drives high leave-without-being-seen (LWBS) rates, limited data on ideal wait times and impact on LWBS rates exist.
  
  
  OBJECTIVE
  We studied the LWBS rates by triage class and target wait times required to achieve various LWBS rates.
  
  
  METHODS
  We conducted a 3-year retrospective analysis of patients presenting to an urban, tertiary, academic, adult emergency department (ED). We divided the 3-year study period into 504 discrete periods by year, day of the week, and hour of the day. Patients of same triage level arriving in the same bin were exposed to similar ED conditions. For each bin, we calculate the mean actual wait time and the proportion of patients that abandoned. We performed a regression analysis on the abandonment proportion on the mean wait time using weighted least squares regression.
  
  
  RESULTS
  A total of 143,698 patients were included for analysis during the study period. The R(2) value was highest for Emergency Severity Index (ESI) 3 (R(2) = 0.88), suggesting that wait time is the major factor driving LWBS of ESI 3 patients. Assuming that ESI 2 patients wait less than 10 minutes, our sensitivity analysis shows that the target wait times for ESI 3 and ESI 4/5 patients should be less than 45 and 60 minutes, respectively, to achieve an overall LWBS rate of less than 2%.
  
  
  CONCLUSIONS
  Achieving target LWBS rates requires analysis to understand the abandonment behavior and redesigning operations to achieve the target wait times.
authors.affiliation: Perlman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Jared
authors.initials: J
authors.lastname: Lucas
authors.affiliation: Operations & Information Management Department, Wisconsin School of Business, University of Wisconsin-Madison, Madison, WI.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Batt
authors.affiliation: Department of Emergency Medicine, University of Pennsylvania, Philadelphia, PA. Electronic address: olanmd@gmail.com.
authors.forename: Olanrewaju A
authors.initials: OA
authors.lastname: Soremekun
mesh_terms: D000328:Adult; D003441:Crowding; D004636:Emergency Service, Hospital / Q000458:organization & administration*; D005260:Female; D006786:Hospitals, Urban; D006801:Humans; D008297:Male; D008875:Middle Aged; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D013997:Time Factors; D014218:Triage; D014850:Waiting Lists