Facility Characteristics Associated with
Racial and Ethnic Disparities in Waiting
Times at U.S. Emergency Departments
Nancy Sonnenfeld1
AcademyHealth Annual Research Meeting
June 26, 2010
1Centers
for Disease Control and Prevention,, National Center for Health Statistics
Disclaimer: This presentation reflects only the views of its authors and are not necessarily those of the Centers for
Disease Control and Prevention.
Co-Authors
Susan M. Schappert,
Centers for Disease Control and Prevention,,
National Center for Health Statistics
Stephen R. Pitts,
Emory University School of Medicine
C
Crowding
di
“A situation in which the identified need for
emergency services outstrips available
resources in the emergency department”1
 May threaten quality including patient safety
 Previous researchers have demonstrated racial
and ethnic disparities in waiting time

1Asplin
et al. Ann Emerg Med. 2003;42:173-180.
Research Objectives
1. Describe racial/ethnic disparities in wait time for
patients
i
off all
ll ages. Assess
A
within
i hi andd across ED
disparities in wait time.
2. Identify hospital/ED characteristics associated with
p on disparities.
p
wait time. Examine their impact
Conceptual Model: ED Crowding
Emergency
Department
Crowding
Ph i l Capacity
Physical
C
it and
d Financial
Fi
i lR
Resources
Data Source
2005-2006 National Hospital Ambulatory Medical Care
Survey,
y, Emergency
g y Department
p
Module ((NHAMCSED)
 annual nationally representative survey of U.S EDs, and
visits
i it to
t them
th
 non-federal hospitals with emergency departments or
outpatient departments
 data are gathered about the ED by interview with an ED
clinic administrator, and about patients/visits by
abstracting records from a random sample of visits
Outcome Variable
Waiting Time
Defined as duration from time of arrival to time
seen by a physician
 By definition,
definition excluded visits where patient died
on arrival or left before being seen (may
underestimate overall wait times)

Patient/Visit Variables
Primary independent variable: patient race and
Hispanic ethnicity
Other: triage status, hour of visit, patient age,
patient sex, expected payment source, arrival by
ambulance
Hospital/ED Variables
Variable
Reason
Percent non
non-Hispanic
Hispanic black, Hispanic
Disparity
ED volume, 4-week observation period
Input
Percent visits with advanced imaging
Throughput
Ownership,
O
hi M
Metropolitan
li location,
l
i
% visits
i i with
ih P
Previous
i
Medicaid/S-CHIP, and uninsured
NHAMCS
ese c
research
Can’t Measure Boarding Well…
…Tried to Control for Output
Variable
Reason
Percent visits six or more hours treatment time Output/
and admitted or transferred
boarding
proxy
Percent visits six or more hours treatment time Throughput
Analytical Approach
Sample Size
63,744 eligible visits to 457 EDs
Waiting
W
iti Time
Ti
 Right skewed distribution
 Medians presented in descriptive analysis
 Variable log-transformed for models (interpret coefficient as % change)
SAS and SAS-callable Sudaan
 Descriptive statistics
 Examined plots and quartile distributions to determine how to specify
continuous variables
 Hybrid fixed effects linear regression models (GEE)
 Too many ED variables; best subsets approach
Median Waiting Time by Race/Ethnicity,
United States,, 2005-2006
Race/Ethnicity
Sample
Size
Median
(95% Confidence
Interval)
Total
63,744
37.9 (35.0-40.8)
Non-Hispanic White
37,421
34.5 (30.9-38.1)
Non-Hispanic Black
13,925
44.3 (40.3-48.2)**
Hispanic
9,300
46.7 (42.7-50.7)**
Asian
1,877
33.6 (27.4-39.9)
Other
1,221
29.8 (23.6-35.9)
**p < .001 Source: National Hospital Ambulatory Medical Care Survey
Racial/Ethnic Differences in Waiting Time,
U it d St
United
States
t 2005-2006
2005 2006
Regression Coefficient (95% Confidence Interval)
U dj
Unadjusted
d
I t
Intercept
t
3 31 (3.24,
3.31
(3 24 33.37)
37)
Overall
Non-Hispanic white
Non Hispanic black
Non-Hispanic
Hispanic
Reference
0 30 (0.22,
0.30
(0 22 0.39)**
0 39)**
0.34 (0.26, 0.41)**
Overall
O
ll adjusted
dj
d for
f
visit characteristics^
3.28 (3.19, 3.37)
Within
Wi
hi andd across
adjusted for visit
characteristics^
3.30 ( 3.22, 3.38)
Reference
0 26 (0.17-0.34)**
0.26
(0 17 0 34)**
0.29 (0.22-0.37)**
Within
Non-Hispanic white
Non-Hispanic black
Hispanic
Reference
0.03 (-0.01, 0.06)
0.08 ( 0.50, 0.12)*
Across (10 percentage point
difference in composition)
22% black and 13% Hispanic
Non-Hispanic black
Hi
Hispanic
i
Reference
0.09 ( 0.06, 0.11)**
0.09 ( 0.06, 0.12)**
Waiting time is log-transformed. ^Adjusted for age, sex, triage assessment, time of arrival, arrival by ambulance, and
expected source of payment. Source: National Hospital Ambulatory Medical Care Survey,** < .001; * p < .05
ED Characteristics Associated with Waiting Time,
United States, 2005-2006
Regression
R
i Coefficient
C ffi i
(95% Confidence Interval)
Intercept
ED volume (per 4 week sampling period)
(1,000 visits)
per 1,000 visit increase
3,100 or more
Percent visits 6 hours or more for treatment
0 -2.39 % (Quartile 1)
2 4 5 09% (Quartile 2)
2.4-5.09%
5.1-8.79% (Quartile 3)
8.8-87.6% (Quartile 4)
3 18 (3.02,
3.18
(3 02 33.33)
33)
Reference
0.24 ((0.17,, 0.32)) **
0.72 (0.51, 0.92) **
-0.28 (-0.41, -0.14) **
-0.25 (-0.39, -0.12) **
-0.20 (-0.31, -0.08) *
Reference
Waiting time is log-transformed. Adjusted for age, sex, race/ethnicity, triage assessment, time of
p
source of payment.
p y
Also adjusted
j
for hospital
p
arrival,, arrival byy ambulance,, and expected
inpatient bed size, ownership, and race and ethnicity of visits.
Source: National Hospital Ambulatory Medical Care Survey,** < .001; * p < .05
Racial/Ethnic Differences in Waiting Time,
United States, 2005-2006
Regression Coefficients
Without ED characteristics
With ED characteristics
Within
Non-Hispanic white
p
black
Non-Hispanic
Hispanic
Reference
0.03 ((-0.01, 0.06))
0.08 ( 0.05, 0.12)**
Reference
0.02 ((-0.01,
0.01, 0.05)
0.07 (0.04, 0.11)**
Across (10 percentage point
difference in composition)
22% black and 13% Hispanic
Non-Hispanic black
Hispanic
Reference
0.09 ( 0.06, 0.11)**
0.09 ( 0.06, 0.12)**
Reference
0.05 (0.03, 0.08)**
0.05 (0.02, 0.08)**
Adjusted for age, sex, triage assessment, time of arrival, arrival by ambulance, and expected
source of payment, ED volume, Percent visits 6 or more hours of treatment, inpatient bed size
and ownershipp
Source: National Hospital Ambulatory Medical Care Survey,** < .001; * p < .05
Main Findings

In U.S. Emergency Departments (EDs), nonHi
Hispanic
i black
bl k andd Hispanic
Hi
i patients
ti t wait
it about
b t
30% longer than non-Hispanic white patients

Most di
M
disparities
i i occur because
b
patients
i
off
different racial/ethnic groups are treated in
different EDs

Even within an individual ED, Hispanic patients
wait about 8% longer
Within individual EDs, non-Hispanic black and
white patients wait about the same amount of time

Main Findings
Of ED characteristics examined, ED volume
mostt strongly
t
l associated
i t d with
ith waiting
iti time
ti
 Long waiting times correlated with prolonged
treatment time
i among all
ll visits
i i regardless
dl off
visit disposition

Limitations
Analysis does not identify factors contributing
to volume and inefficiency
 Cannot distinguish between
 factors affecting
g all aspects
p
of crowding
g
 role of boarding
BUT adjustment
dj
for
f throughput/output
h
h /
does
d
not substantially diminish volume-waiting
time association

Policy Implications
To address disparities in waiting time, ED
volume appears
pp
important
p
 Boarding or inefficiencies during treatment
may explain some disparities; better measures
needed to understand this problem
 Much remains unexplained
