title: Measures of crowding in the emergency department: a systematic review.
abstract: OBJECTIVE
  Despite consensus regarding the conceptual foundation of crowding, and increasing research on factors and outcomes associated with crowding, there is no criterion standard measure of crowding. The objective was to conduct a systematic review of crowding measures and compare them in conceptual foundation and validity.
  
  
  METHODS
  This was a systematic, comprehensive review of four medical and health care citation databases to identify studies related to crowding in the emergency department (ED). Publications that "describe the theory, development, implementation, evaluation, or any other aspect of a 'crowding measurement/definition' instrument (qualitative or quantitative)" were included. A "measurement/definition" instrument is anything that assigns a value to the phenomenon of crowding in the ED. Data collected from papers meeting inclusion criteria were: study design, objective, crowding measure, and evidence of validity. All measures were categorized into five measure types (clinician opinion, input factors, throughput factors, output factors, and multidimensional scales). All measures were then indexed to six validation criteria (clinician opinion, ambulance diversion, left without being seen (LWBS), times to care, forecasting or predictions of future crowding, and other).
  
  
  RESULTS
  There were 2,660 papers identified by databases; 46 of these papers met inclusion criteria, were original research studies, and were abstracted by reviewers. A total of 71 unique crowding measures were identified. The least commonly used type of crowding measure was clinician opinion, and the most commonly used were numerical counts (number or percentage) of patients and process times associated with patient care. Many measures had moderate to good correlation with validation criteria.
  
  
  CONCLUSIONS
  Time intervals and patient counts are emerging as the most promising tools for measuring flow and nonflow (i.e., crowding), respectively. Standardized definitions of time intervals (flow) and numerical counts (nonflow) will assist with validation of these metrics across multiple sites and clarify which options emerge as the metrics of choice in this "crowded" field of measures.
authors.affiliation: Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY. ula.hwang@mountsinai.org
authors.forename: Ula
authors.initials: U
authors.lastname: Hwang
authors.forename: Melissa L
authors.initials: ML
authors.lastname: McCarthy
authors.forename: Dominik
authors.initials: D
authors.lastname: Aronsky
authors.forename: Brent
authors.initials: B
authors.lastname: Asplin
authors.forename: Peter W
authors.initials: PW
authors.lastname: Crane
authors.forename: Catherine K
authors.initials: CK
authors.lastname: Craven
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Epstein
authors.forename: Christopher
authors.initials: C
authors.lastname: Fee
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Handel
authors.forename: Jesse M
authors.initials: JM
authors.lastname: Pines
authors.forename: Niels K
authors.initials: NK
authors.lastname: Rathlev
authors.forename: Robert W
authors.initials: RW
authors.lastname: Schafermeyer
authors.forename: Frank L
authors.initials: FL
authors.lastname: Zwemer
authors.forename: Steven L
authors.initials: SL
authors.lastname: Bernstein
mesh_terms: D001509:Bed Occupancy / Q000706:statistics & numerical data; D003441:Crowding; D017598:Efficiency, Organizational; D004636:Emergency Service, Hospital / Q000458:organization & administration / Q000706:statistics & numerical data; D006801:Humans; D019984:Quality Indicators, Health Care; D014850:Waiting Lists; D057188:Workflow