Context There is growing pressure to avoid hospitalizing emergency department
patients who can be treated safely as outpatients, but this strategy depends
on timely access to follow-up care.
Objective To determine the association between reported insurance status and access
to follow-up appointments for serious conditions that are commonly identified
during an emergency department visit.
Design, Setting, and Participants Eight research assistants called 499 randomly selected ambulatory clinics
in 9 US cities (May 2002–February 2003) and identified themselves as
new patients who had been seen in an emergency department and needed an urgent
follow-up appointment (within 1 week) for 1 of 3 clinical vignettes (pneumonia,
hypertension, or possible ectopic pregnancy). The same person called each
clinic twice using the same clinical vignette but different insurance status.
Main Outcome Measure Proportion of callers who were offered an appointment within a week.
Results Of 499 clinics contacted in the final sample, 430 completed the study
protocol. Four hundred six (47.2%) of 860 total callers and 277 (64.4%) of
430 privately insured callers were offered appointments within a week. Callers
who claimed to have private insurance were more likely to receive appointments
than those who claimed to have Medicaid coverage (63.6% [147/231] vs 34.2%
[79/231]; difference, 29.4 percentage points; 95% confidence interval, 21.2-37.6; P<.001). Callers reporting private insurance coverage
had higher appointment rates than callers who reported that they were uninsured
but offered to pay $20 and arrange payment of the balance (65.3% [130/199]
vs 25.1% [50/199]; difference, 40.2; 95% confidence interval, 31.4-49.1; P<.001). There were no differences in appointment rates
between callers who claimed to have private insurance coverage and those who
reportedly were uninsured but willing to pay cash for the entire visit fee
(66.3% [132/199] vs 62.8% [125/199]; difference, 3.5; 95% confidence interval
−3.7 to 10.8; P = .31). The median
charge was $100 (range, $25-$600). Seventy-two percent of clinics did not
attempt to determine the severity of the caller’s condition.
Conclusions Reported insurance status is associated with access to timely follow-up
ambulatory care for potentially serious conditions. Having private insurance
and being willing to pay cash may not eliminate the difficulty in obtaining
urgent follow-up appointments.
In 2005 US residents will make about 114 million visits to hospital
emergency departments (EDs).1 More than 80%
will be treated and discharged with a recommendation for follow-up care. Patients
who have a primary care clinician are generally referred back to their usual
source of care for follow-up. However, many ED patients, both insured and
uninsured, either lack an established relationship with a primary care clinician
or have reported difficulty obtaining timely appointments with their usual
source of care.2 For those with a potentially
serious condition that requires urgent follow-up, timely access to outpatient
care is essential to avoid the costs of hospitalization or an adverse outcome.
It is difficult to measure access to outpatient care objectively. Surveys
of private physician offices and ambulatory clinics are prone to social desirability
bias, and the validity of patient surveys may be compromised by selection,
recall, and nonresponse bias.3 In 1994, the
Medicaid Access Study Group4 circumvented these
problems by training research assistants to pose as patients seeking care
for 1 of 3 minor but physically uncomfortable health problems. In the 9 cities
involved in that study, only 44% of callers who reported that they were covered
by Medicaid could secure an appointment at any point and only 8% could get
an appointment within 2 working days without agreeing to pay a substantial
cash co-payment.
It is not known whether Medicaid and uninsured patients who have been
evaluated in an ED and found to have an urgent or potentially dangerous health
problem face similar barriers to outpatient care. To help provide information
on this issue, we adopted the same approach used by the Medicaid Access Study
Group4 but used much more serious clinical
scenarios. Our primary goal was to determine whether insurance status was
associated with the timing and availability of an appointment for urgent ambulatory
follow-up care after reportedly being discharged from the ED. Our secondary
goal was to assess overall access to follow-up care for patients reportedly
treated and released from the ED with a potentially serious health condition.
To achieve population and geographic diversity, 9 US cities were selected.
The sampling frame was developed using the ambulatory care follow-up lists
of EDs located in each city. In consultation with the study site directors,
a convenience sample of local EDs was identified and a list of follow-up clinics
was generated using all the condition-appropriate follow-up clinics from each
ED. For the purpose of this study, clinic was defined
as any site where appropriate follow-up physician care was available. The
sampling frame included hospital and health system clinics, community clinics,
and private physician offices. From this list, follow-up clinics were randomly
sampled for the survey. Safety net clinics were identified by asking site
directors to identify where they would refer an uninsured patient or a Medicaid
beneficiary. Because the number of these clinics was limited, all safety net
clinics were contacted.
Calls were made from a central computer-assisted telephone interview
(CATI) center (University of Chicago Survey Laboratory) by graduate students
who were hired to pose as patients. Callers were trained using standard interview
questions and data collection forms that were developed during a pretest phase
of the study. To ensure reproducibility, all 8 callers were supervised throughout
the study and a subset of calls was monitored.
Three clinical conditions were chosen based on the need for urgent follow-up
care: community-acquired pneumonia (pneumonia severity index class III),5 asymptomatic accelerated hypertension with a diastolic
blood pressure greater than 110 mm Hg, and possible ectopic pregnancy (low
abdominal pain, vaginal bleeding, and an indeterminate ultrasound). Women
using the “possible ectopic pregnancy” vignette contacted only
obstetrics and gynecology and family medicine clinics. Men used the pneumonia
and hypertension vignettes. The survey center designated clinics as out of scope if the clinic employee who handled the call
reported that the clinic did not provide care for the clinical condition.
For example, a family medicine clinic that did not accept obstetric patients
was judged to be out of scope for the possible ectopic pregnancy vignette.
When an out-of-scope clinic was identified, it was excluded from the analysis
and a replacement clinic was randomly selected from the sampling frame.
Each clinic in the study was called twice by the same caller using the
same scripted clinical vignette. None of the clinics in the final analysis
was omitted and no clinic was sampled for more than 1 comparison. During 1
call, the caller claimed to have private insurance; on the other call, the
caller either reported that he/she was a Medicaid beneficiary or was uninsured.
The order of the calls was randomly assigned by the computer-assisted telephone
interview system. To minimize the likelihood that a caller would be identified,
the survey center required at least 14 days between the first and second calls.
Furthermore, the survey center blocked caller identification on all outgoing
calls.
If a clinic refused to complete its appointment screening process without
a specific insurance number or Social Security number, it was classified as
“unable to complete the protocol.” If a clinic’s telephone
number was incorrect or disconnected, research assistants sought to correct
any clerical errors. If the incorrect telephone number was verified as the
number patients were receiving from the referring EDs, this clinic was classified
as a “wrong number” and a replacement clinic was randomly chosen.
Failed appointments due to incorrect telephone numbers were excluded from
the analysis.
Callers began each call stating they had been seen in a community ED
the previous night and needed a follow-up appointment. Callers did not use
the name of the local ED in their initial appointment request; however, when
requested they provided it. If the caller was offered an appointment more
than a week after the call, the caller asked to be seen sooner and stated
that the emergency physician had urged the patient to be seen as soon as possible.
Callers used details from their clinical condition to emphasize the importance
of obtaining an urgent appointment (eg, “I went to the ER last night
for a cough and they told me I had pneumonia. I’m a diabetic and I’ve
had some kidney problems, so the ER doctor wanted me to follow up. I need
to make an appointment.”) Whenever a caller who claimed to be uninsured
was offered an appointment, he/she asked if cash would be required at the
time of the visit and if so, how much. If the required amount exceeded $20,
the caller offered to bring $20 to the appointment and arrange a plan to pay
the balance later. If callers were unable to obtain an appointment, they asked
the clinic staff why they could not be seen.
Callers used a series of standard responses when they were asked for
specific insurance information, identification numbers, or both. These phrases
were developed during the pilot phase of the study and were selected to maximize
the likelihood of a successful appointment. For example, callers stated that
they did not have their insurance card with them during the call, but that
their insurance type allowed them to choose their own provider and that they
would bring their identification card with them to the appointment. Callers
did not provide any false identification numbers to clinic staff.
The primary outcome was the percentage of callers by insurance status
who successfully secured a follow-up appointment within a week of their call.
Because of the data collection protocol, we also recorded appointment success
rates for uninsured callers both with and without the $20 cash restriction
at the time of the appointment. If a clinic offered an uninsured caller an
appointment within a week but required more than $20 to arrange the appointment,
that call would be classified as a successful appointment for an uninsured
caller with unlimited cash payment and a failed appointment for an uninsured
caller who was limited to a $20 payment at the time of the appointment. The
a priori definition of a successful appointment for an uninsured patient was
an offered appointment within 7 days with a maximum $20 cash payment and an
offer to pay the balance later. To avoid blocking appointments for actual
patients, all appointments were cancelled at the end of each call.
To protect the confidentiality of clinics and their staff, all clinic
identifiers were removed from the study database prior to the analysis. The
only clinic-level data retained in the analysis database was the safety net
status of the clinic.
The unit of analysis was the clinic, and appointment rates were compared
using the paired calls to each clinic. One analysis compared appointment rates
for callers claiming to have private insurance vs Medicaid coverage; the other
compared appointment rates for callers claiming to have private insurance
vs no insurance coverage. Significance was determined using McNemar’s
test of paired proportions (α = .05). Assuming a baseline
appointment rate of 60% in the privately insured group, we calculated that
200 clinic pairs would be needed to detect a 20% difference in appointment
rates with 90% power after adjusting for differences by vignette and city.
Because the study did not involve actual care of patients and the confidentiality
of contacted clinics was closely guarded, it was approved for nationwide administration
by the institutional review boards of the principal coinvestigators (B.R.A.,
K.V.R.) and the survey center (K.V.R.). All analyses were conducted using
STATA version 8.2 (StataCorp LP, College Station, Tex).
During the 10-month study period (May 2002 through February 2003), the
survey center attempted to contact 604 clinics (Figure). Seventy-seven clinics (12.7%) were deemed out of scope
and were excluded from further analysis. Of the remaining 527 clinics, 28
(5.3%) were excluded because an incorrect telephone number was provided by
the referring ED. Of the 499 clinics in the final survey sample, callers were
unable to complete the study protocol with 69 clinics (13.8%). The remaining
430 clinics completed the study protocol (response rate, 430 [86.2%] of 499).
It took the survey center an average of 2 calls (range, 1-7 calls) to complete
the study protocol for each insurance type. Ninety-eight percent of the clinics
completed a financial screening process with the callers.
Of the 430 clinics with 2 completed contacts (860 completed appointment
attempts), 406 (47.2%) of 860 contacts resulted in an appointment within 7
days. For the private insurance vs Medicaid comparison, 231 clinics were contacted
twice. A caller claiming to have private insurance was more likely to secure
a prompt follow-up appointment than when the same caller claimed to be covered
by Medicaid (63.6% [147/231] vs 34.2% [79/231]; difference, 29.4 percentage
points; 95% confidence interval [CI], 21.2-37.6; P<.001).
For the private insurance vs uninsured comparison, 199 clinics were contacted
twice. Again, callers had higher appointment rates when they claimed to be
privately insured than when the same callers stated they were uninsured and
offered to bring $20 at the time of the visit (65.3% [130/199] vs 25.1% [50/199];
difference, 40.2 percentage points; 95% CI, 31.4-49.1; P<.001). If callers claiming to be uninsured could pay cash for
the entire charge at the time of their visit, there was no difference in rates
of securing a timely appointment (private insurance vs uninsured paying cash,
66.3% [132/199] vs 62.8% [125/199]; difference, 3.5 percentage points; 95%
CI, −3.7 to 10.8; P = .31). The median
cash charge for a follow-up visit was $100 (range, $25-$600).
Table 1 reports survey results
by clinic type, clinical vignette, and city. Access to care within a week
of contact did not differ by clinic type (safety net vs nonsafety net) for
Medicaid callers (37.5% vs 33.7%; difference, 3.8 percentage points; 95% CI,−14.0
to 21.7; P = .67) or uninsured callers
(33.3% vs 23.8%; difference, 9.5 percentage points; 95% CI, −8.2 to
27.2; P = .29) when uninsured callers limited
their available cash to $20 at the time of the visit. When all offered appointments
were considered (even those beyond the 7-day time frame), safety net clinics
were only marginally more likely to provide a follow-up visit to Medicaid
callers than nonsafety net clinics (62.5% vs 44.7%; difference, 17.8 percentage
points; 95% CI, −0.9 to 36.4; P = .06).
Safety net clinics were less likely than nonsafety net clinics to offer a
timely appointment to a privately insured caller (50.8% vs 66.6%; difference
−15.8 percentage points; 95% CI, −28.9 to −2.6; P = .02).
In 72% of the completed cases, the callers did not believe the clinic
staff had tried to discover the nature or seriousness of their clinical condition.
The clinical vignette used in a call was not associated with appointment success.
There was no appreciable city-by-city variability in access to follow-up care
for privately insured or uninsured patients; however, access to follow-up
care for Medicaid callers differed markedly among cities.
Callers recorded the reasons they were refused appointments (Table 2). Callers who claimed to have Medicaid
coverage were generally told that the clinic did not accept Medicaid; this
was true for 74.6% (91/122) of the Medicaid callers who were refused appointments.
Callers claiming to be privately insured who were refused appointments, in
contrast, were generally told either that the clinic was not accepting new
patients at that time (31.1% [19/61] of callers) or that no appointment times
were available soon enough to meet the caller’s needs (23.0% [14/61]
of callers). Of the 199 callers who claimed to be uninsured, 125 were initially
offered an appointment under the assumption that they would pay cash for their
visit. Clinics subsequently refused appointments to 75 of these 125 callers
when a request was made to pay $20 at the time of the visit and arrange payment
for the balance.
The findings in this study raise concerns about access to outpatient
care. The nationwide trend toward more aggressive outpatient care of ED patients
with potentially serious conditions raises important questions—is timely
access to follow-up care available to those who need it? If so, how is access
influenced by the patient’s insurance coverage? The conditions we selected—accelerated
hypertension, pneumonia severity index class III pneumonia, and possible ectopic
pregnancy—clearly warrant timely follow-up. The challenge faced by the
callers in our study is no different than that faced by millions of discharged
ED patients each year—finding a clinic or physician who is able to see
them for a newly diagnosed health problem.
Insurance coverage is widely recognized as an enabling factor for accessing
health care services. The Institute of Medicine recently documented that in
the United States the uninsured get about half of the medical care of those
who are insured, and as a result, those without insurance tend to have more
illness and shorter life expectancy than those with health insurance.6-8 Furthermore, the committee
noted that uninsurance may have important “spillover effects”
that compromise the economic viability of health care clinicians and institutions,
particularly in communities with large numbers of uninsured citizens.9 If this is true, the consequences of uninsurance may
extend beyond the uninsured and hinder access to care for insured and uninsured
alike.
In light of known relationships between health insurance and access
to care in the United States, it is not surprising that callers who are uninsured
face barriers to securing timely access to follow-up care. It may be surprising
to some that appointment rates for callers covered by Medicaid were only marginally
better than those for uninsured callers who offered to pay $20. This raises
questions about the adequacy of Medicaid reimbursement for outpatient care.
We noted wide disparities in the rate of follow-up appointments granted to
Medicaid callers by city (from a low of 8% in Denver to a high of 65% in Minneapolis/St.
Paul). Although we did not collect Medicaid reimbursement data and cannot
directly explain these differences, variation in Medicaid payment rates may
be contributing to the observed differences. Skaggs et al10 reached
this conclusion in a study of access to orthopedic care for pediatric Medicaid
beneficiaries in California. Currie et al11 found
that states that increased their Medicaid fee ratios experienced small but
significant reductions in infant mortality. These observations cast doubt
on the wisdom of reducing payments to maintain the solvency of state Medicaid
programs because doing so may compromise beneficiaries’ access to care.
Our results illustrate how the anticipated rates of reimbursement may
influence access to care. If uninsured callers were able to pay the full cash
charge at the time of their visit, they were granted timely appointments at
the same rate as callers with private insurance. However, it is unlikely that
many uninsured patients could readily pay the median requested amount of $100
for a follow-up visit, let alone the maximum requested charge of $600. Regardless
of insurance status, 98% of clinics contacted in this study screened callers
to determine insurance status, whereas only 28% attempted to determine the
severity of the caller’s condition.
Callers posing as uninsured or Medicaid patients were no more likely
to secure a timely appointment from safety net clinics than from nonsafety
net clinics. There are 2 potential explanations for this observation. One
is that these clinics are so financially strained that they cannot afford
to accommodate poorly paying patients. Alternatively, the capacity of these
clinics may be so limited that they can no longer accommodate new patients
within the 1-week time frame used in this study. That privately insured callers
experienced considerable difficultly getting a timely appointment from safety
net clinic suggests that the latter explanation is more likely. The lower
appointment rate at safety net clinics for callers who claimed to be privately
insured also may reflect the mission of some safety net clinics to serve only
the poor or uninsured.
The disparities we noted in access to care among uninsured, Medicaid,
and privately insured patients are consistent with other reports on the impact
of health insurance status and access to care. However, one third of the clinics
we contacted could not provide access to a new patient with private insurance
within a week, even though the callers stated that they had just been seen
in a local ED, diagnosed with an urgent health problem, and advised to arrange
follow-up care as quickly as possible. This suggests that the challenge of
securing timely access to outpatient care extends beyond the ranks of the
uninsured. Because our callers were trained graduate students who developed
significant expertise with the appointment scheduling process, our results
may represent a best-case scenario for new patients at follow-up clinics.
Timely follow-up care is necessary to prevent adverse outcomes and reduce
unnecessary hospitalizations. Ambulatory care access barriers create challenges
for both emergency patients and clinicians. It may be unsafe to discharge
a patient with a potentially serious health problem if timely and appropriate
follow-up cannot be ensured at the time of the ED visit. However, if emergency
physicians err on the side of caution and admit more patients with “borderline”
diagnoses, this will impose considerable costs on patients, their families,
employers, hospitals, and insurance plans. Alternatively, emergency physicians
may ask their patients to return to the ED for ongoing care when traditional
follow-up care cannot be guaranteed, but this practice could contribute to
ED crowding and inefficient use of ED resources.
Although emergency physicians routinely refer discharged patients to
follow-up clinicians, the appropriate timing of follow-up appointments for
discharged ED patients has not been studied widely. It is possible that the
routine recommendation to follow-up “within a week” is saturating
the capacity of ambulatory clinics, thereby preventing timely access to care
for patients who truly require urgent follow-up care. To avoid this issue
we carefully selected conditions for which timely follow-up care is warranted.
Nevertheless, evidence-based guidelines that prioritize the need for follow-up
care after ED discharge would be a helpful resource for both clinicians and
patients.
Our findings are of particular concern given the progress some systems
have made with improving timely access to care. The advanced access model
is an approach to ambulatory clinic scheduling that offers same-day appointments
to patients.12,13 It has been
shown to reduce delays and increase the continuity of primary care for patients
with chronic conditions.14 Although we do not
know whether the advanced access model was in place at any of the study clinics,
it appears that advanced access may be the exception rather than the rule
in US ambulatory clinics. The widespread use of this model could improve the
availability of timely follow-up care for ED patients.
Because our study required the use of deception, we conducted it with
a number of ethical safeguards. The telephone calls to office staff were made
in a routine manner that attempted to minimize time spent on the telephone.
When an appointment was secured, it was cancelled at the end of the call so
the appointment slot would be available for an actual patient. The study investigators
were blinded to the identities of the clinics and staff who handled these
calls. After data collection was completed, we mailed debriefing letters to
all 1206 clinics in the sampling frame. This letter disclosed the nature of
the study and reported results by city. Clinic managers and physicians were
advised that their clinic might have been contacted during the study, and
they were invited to contact us with any questions or concerns. We did not
receive any replies to this debriefing letter.
Our study is limited in several respects. The most important limitation
is that all of our callers were, by definition, posing as new patients at
every clinic they contacted. It is therefore inappropriate to extrapolate
our findings to patients who have a usual source of care. These patients likely
would have less difficulty securing timely appointments for follow-up care
and often may be able to bypass clinic receptionist staff to speak directly
with their physician. However, this does not negate the importance of our
findings for several reasons. First, an analysis of the Medicare Expenditure
Panel Survey indicates that even those ED patients who have a usual source
of care report difficulties scheduling an appointment or experience long waiting
times for an appointment.2 Although this analysis
did not address the need for urgent appointments, it does illustrate that
having a usual source of care does not guarantee timely access to care. Second,
even if appointment rates are higher for patients with a usual source of care,
the disparities in appointment rates we observed across insurance types may
still persist. And third, even though most patients are fortunate to have
a usual source of care, tens of millions of US residents do not have a relationship
with a primary care clinician.15
Because our callers were not actual patients, they could not complete
the appointment process if a specific health insurance policy or Social Security
number was required. However, 86% of clinics completed the survey protocol
without requiring this information. We believe that the loss of these clinics
did not appreciably alter our findings. If anything, the inclusion of these
clinics would result in even greater disparities in appointment rates, since
clinics that require this information during the telephone interview may be
even less likely to offer appointments to callers claiming to be uninsured
or have Medicaid coverage. The 9 US cities we surveyed were chosen for geographic
and ethnic diversity. We did not, however, obtain a random sample of clinics
from the entire population of US health care clinicians. Therefore our findings
cannot be generalized to rural communities. Many emergency physicians contact
on-call physicians directly from the ED to ensure that selected patients have
access to timely follow-up care. Although we agree that this practice is often
effective, it is not a practical system-wide solution given the volume of
patients in most EDs and the limited number of on-call physicians.16
Our sample included a number of incorrect or disconnected telephone
numbers. We confirmed that these numbers were being provided to patients referred
by EDs in these communities. Since this was not an isolated phenomenon or
one that was limited to a single city, it probably reflects the experience
of many ED patients seeking follow-up care and is another operational problem
that deserves attention. Finally, it is important to note that the offer of
a follow-up appointment does not guarantee appropriate care. Likewise, failure
to authorize a follow-up appointment over the telephone does not mean a clinic
would have refused care if the patient presented in person. However, it is
unlikely that many patients would seek care in person if they were refused
an appointment over the telephone.
These study findings suggest that reported insurance status influences
access to follow-up appointments for patients with conditions requiring urgent
ambulatory follow-up care. While this is particularly true for Medicaid beneficiaries
and the uninsured, some privately insured patients and uninsured patients
paying cash may experience considerable difficulty obtaining urgent appointments.
Although the ultimate consequences of these access barriers are not known,
they may result in patients’ delaying needed follow-up care, risking
adverse outcomes, or requiring additional emergency care or hospitalization.
Corresponding Author: Brent R. Asplin, MD,
MPH, Department of Emergency Medicine, Regions Hospital, 640 Jackson St, St
Paul, MN 55101 (Brent.R.Asplin@HealthPartners.com).
Author Contributions: Dr Asplin had full access
to all of the data in the study and takes responsibility for the integrity
of the data and the accuracy of the data analysis. Dr Rhodes served as the
principal co-investigator throughout the design, implementation, analysis,
and reporting of the study.
Study concept and design: Asplin, Rhodes, Lurie,
Carlin, Kellermann.
Acquisition of data: Asplin, Rhodes.
Analysis and interpretation of data: Asplin,
Rhodes, Levy, Lurie, Crain, Carlin, Kellermann.
Drafting of the manuscript: Asplin, Rhodes,
Kellermann.
Criticalrevision of the
manuscript for important intellectual content: Asplin, Rhodes, Levy,
Lurie, Crain, Carlin, Kellermann.
Statistical analysis: Asplin, Rhodes, Levy,
Lurie, Crain, Carlin.
Obtained funding: Asplin, Rhodes, Lurie.
Administrative, technical, or material support:
Asplin, Rhodes, Kellermann.
Study supervision: Asplin, Rhodes, Lurie, Kellermann.
Financial Disclosures: None reported.
SiteDirectors:Phoenix, Ariz: Brian Tiffany, MD, PhD, Maricopa Medical
Center; Los Angeles: Deirdre Anglin, MD, MPH, Los
Angeles County, University of Southern California Medical Center; Denver, Colo: Debra Houry, MD, MPH, Emory University; Jacksonville: Robert Wears, MD, MS, University of Florida; Atlanta, Ga: Arthur L. Kellermann, MD, MPH, Emory University; Chicago, Ill: Karin V. Rhodes, MD, University of Chicago
Hospitals; Minneapolis/St Paul, Minn: Brent R. Asplin,
MD, MPH, Regions Hospital; New York, NY: Lynne D.
Richardson, MD, Mt Sinai Medical Center; Dallas/Ft Worth: Gregory L. Larkin, MD, MS, MSPH, University of Texas Southwestern
Medical Center.
Funding/Support: Project costs were funded
by the Henry J. Kaiser Family Foundation. Dr Asplin's work was supported by
grant K08-HS13007 from the Agency for Healthcare Research and Quality.
Role of the Sponsors: The project manager from
the Kaiser Family Foundation assisted the investigators with the study methods
and interpretation of the data. The project manager did review the manuscript
prior to publication; however, the study investigators take full responsibility
for the content of the manuscript.
Acknowledgment: We thank Catherine Hoffman,
ScD, Henry J. Kaiser Family Foundation; Martha Van Haitsma, University of
Chicago Survey Lab; Shannon O’Keefe, University of Vermont Medical School;
Shelly Feaver, Regions Hospital Department of Emergency Medicine; and the
site directors for their dedicated assistance with the study. We also thank
the staff at the University of Chicago Survey Lab for their expertise throughout
the study.
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