Facility Characteristics Associated with
Racial and Ethnic Disparities in Waiting
Times at U.S. Emergency Departments
Nancy Sonnenfeld,1 Susan M. Schappert,1
Stephen R. Pitts2 ,
AcademyHealth Annual Research Meeting
June 28, 2010
1Centers
for Disease Control and Prevention,, National Center for Health Statistics
University School of Medicine
Disclaimer: This presentation reflects only the views of its authors and are not necessarily those of the Centers for
Disease Control and Prevention.
2Emory
W i i for
Waiting
f Treatment
T
May threaten quality including patient safety
 Previous researchers have demonstrated racial
and ethnic disparities
p

Research Objectives

Describe racial/ethnic disparities in waiting time

Assess within and across ED disparities in waiting
time

Identify hospital/ED characteristics associated with
waiting time

Examine their impact on disparities.
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 a
clinic administrator, and about visits by abstracting
records from a random sample
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)

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
R
Regression
i Coefficients
C ffi i
Without ED characteristics
With ED characteristics
Within
Non-Hispanic white
Non-Hispanic black
Hispanic
Reference
0.03 (-0.01, 0.06)
0.08 ( 0.05, 0.12)**
Reference
0.02 (-0.01, 0.05)
)
0.07 ((0.04,, 0.11)**
Across (10 percentage
point difference in
composition)
22% black and 13%
Hispanic
Non-Hispanic
p
black
Hispanic
Reference
0.09 ( 0.06, 0.11)**
0.11)
0.09 ( 0.06, 0.12)**
Reference
0.05 (0.03, 0.08)**
0.08)
0.05 (0.02, 0.08)**
Adjusted for age,
age sex,
sex triage assessment,
assessment time of arrival
arrival, arrival by ambulance,
ambulance and expected source of payment
payment, ED volume
volume,
Percent visits 6 or more hours of treatment, inpatient bed size and ownership
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
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
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


C t t me att nls2@cdc.gov
Contact
l 2@ d