Date of Award


Degree Type


Degree Name

Master of Science


Epidemiology and Biostatistics


Dr. Greg Zaric

Second Advisor

Dr. Amardeep Thind

Third Advisor

Dr. John Dreyer


BACKGROUND: The Emergency Department (ED) plays an important role in the health care safety net, but its ability to deliver care is compromised due to crowding. This is the major issue currently facing emergency care in Canada. OBJECTIVE: The aim of this study is to determine whether the length of stay (LOS) in the ED affects subsequent hospital outcomes for patients admitted through the ED. METHODS: This was a retrospective study using London Health Science Centre (LHSC) administrative data from April 2006 to April 2007. Three databases were linked to gather information on patient characteristics, health outcomes, and cost of care. There were 15,959 ED visits that led to subsequent admissions. 13,460 ED visits made by adult patients at either University Hospital or Victoria Hospital were included. The predictor variable was ED LOS. The primary outcomes of interest were hospital LOS in days and total hospital cost. Correlation coefficients were used to characterize the relationship of ED LOS with hospital LOS and costs. We fitted log normal models for each outcome: one with ED LOS expressed as a continuous variable; one using 8 hour ED LOS to define delayed care; and the last model with ED LOS expressed as an ordinal variable using quartiles. Multivariate statistical analyses were performed using SAS (version 9.1.3,

SAS Institute, Inc.). RESULTS: When ED LOS is defined as a binary variable using an 8 hour cutoff, 31% of patients (n=4,198) experienced delayed care. On average, delayed care in the ED is associated with a 7.2% increase in inpatient LOS and a 4.8% increase in inpatient cost. When ED LOS is modeled continuously, each additional hour of ED LOS adds 1.1% to inpatient LOS and 0.86% to inpatient cost. All calculations were adjusted for age, sex,


ED triage urgency, arrival by ambulance, admission to ICU or surgery, site of ED, and case mix group. We estimated that these delays resulted in an additional 3,038 inpatient days and $2,268,014 hospital cost. CONCLUSION: Delays in the ED are associated with increased inpatient LOS and inpatient cost. As such, improving patient flow through the ED may reduce hospital costs.



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