(Stroke. 1996;27:801-806.)
© 1996 American Heart Association, Inc.
Articles |
From the Center for Health Policy Research and Education (L.B.G., A.J.B., D.B.M., P.W.D., G.P.S.) and the Divisions of Neurology (L.B.G.) and General Internal Medicine (D.B.M.), Department of Medicine, Duke University, and the Division of Neurology (L.B.G.), Durham Department of Veterans Affairs Medical Center, Durham, NC; the Research Triangle Institute (A.J.B.), Research Triangle Park, NC; and the Center on Aging, University of Kansas (P.W.D.) (Kansas City).
Correspondence to Larry B. Goldstein, MD, Box 3651, Duke University Medical Center, Durham, NC 27710. E-mail golds004@mc.duke.edu.
| Abstract |
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Methods Between August 1993 and February 1994, we surveyed the stroke prevention practices of a stratified random sample of 2000 US physicians. The survey queried the perceived availability and use of diagnostic studies and surgery for specific types of patients who might be considered candidates for CE.
Results Of eligible physicians, 67% (n=1006) completed the survey. Seventy percent reported that they always or often obtain carotid ultrasonography for evaluation of patients with asymptomatic bruits; 89% do so in patients with recent transient ischemic attack or minor stroke (P<.001). For asymptomatic patients, 13% always or often obtain a cerebral angiogram if carotid ultrasonography indicates 50% to 70% stenosis versus 33% if carotid ultrasonography indicates >70% stenosis (P<.001). For asymptomatic patients with >70% stenosis, a cerebral angiogram was reported as seldom or never used by 42% of physicians who viewed the test as readily available versus 67% if cerebral angiography was perceived as not readily available (P=.005). Multinomial multiple logistic regression analysis showed that symptom status, the degree of stenosis, perceived availability of CE, and physician specialty independently contributed to the explained variance in the reported use of CE (P<.001). The odds of performing CE were approximately four times greater in patients with recent symptoms compared with asymptomatic patients (P<.001) and four times greater in patients with >70% stenosis compared with patients with 50% to 70% stenosis (P<.001). Physicians who perceived CE as not being readily available were one third as likely to report using the procedure compared with physicians who reported having ready access (P=.004). CE was reported as being always or often used by more than 80% of neurologists and surgeons but by only about half of internists and noninternist primary care physicians for patients with newly symptomatic high-grade stenosis (P<.001). Almost one in four noninternist primary care physicians responded that they would seldom or never use CE for these patients.
Conclusions These data show that (1) symptom status and degree of carotid artery stenosis strongly influence the reported frequency with which CE is used by practicing physicians; (2) the perceived availability of cerebral angiography and CE significantly affects their reported frequency of use; and (3) physician specialty significantly influences the reported frequency of use of CE.
Key Words: carotid endarterectomy cerebral angiography duplex scanning stroke prevention
| Introduction |
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Despite the wealth of clinical information concerning the use of CE, there are few data available examining how practicing physicians evaluate their patients and use the procedure. The US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke was designed to address these questions.8 An initial report was devoted to a description of the survey methodology, physician and practice characteristics, the perceived availability of basic and advanced stroke prevention services, and the reported use of basic stroke prevention strategies. Carotid ultrasonography, a key test in the diagnostic evaluation of patients being considered for CE, was reported as being readily available by at least 90% of physicians. MR angiography, a relatively new technique, was perceived as being readily available by 68% of respondents. Surprisingly, 12% of physicians reported cerebral arteriography and 10% reported CE as not being readily available. Multiple logistic regression analyses showed that the perceived availability of services varied with physician specialty (noninternist primary care, internal medicine, neurology, or surgery), practice location (nonmetropolitan, small metropolitan, or large metropolitan area), and for CE, region of the country (South, North Central, Northeast, or West). The odds of CE being reported as readily available were approximately 2.5 to 3.5 times greater for physicians practicing in the North Central, Northeast, and Western regions of the United States compared with those practicing in the South, independent of practice setting and specialty.
In addition to these general questions, the survey queried the use of diagnostic tests and CE through a series of specific patient scenarios. The present analyses were designed to determine both how practicing physicians approach the diagnosis and surgical treatment of potential CE candidates and how variables such as physician specialty, practice location, region of the country, and perceived availability of services influence these decisions.
| Methods |
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The self-administered questionnaire included 23 items and was divided into two distinct parts. The first part of the questionnaire consisted of items that described physician and practice characteristics and the availability of selected procedures and tests. The second part of the questionnaire consisted of 12 patient scenarios. These included several vignettes that probed the reported use of diagnostic modalities and surgery in potential CE candidates (eg, patients without contraindications for CE). Physicians were asked how frequently they would obtain carotid ultrasonography or cerebral angiography in specific clinical settings and whether they would either perform CE or refer for surgery asymptomatic and symptomatic patients subsequently found to have moderate (50% to 70%) or high-grade (>70%) stenosis of the extracranial CA.
To simplify the analyses, the responses of family practice specialists and general practice physicians (noninternist primary care physicians) were combined as "primary care," general internal medicine physicians and internal medicine subspecialists were combined as "internal medicine," and neurosurgeons and vascular surgeons were combined as "surgery." The physicians reported using diagnostic procedures or CE always, often, sometimes, seldom, or never in a given clinical setting. Because the categorizations do not represent a meaningful difference in clinical practice and to further simplify the analyses, the responses "always" and "often" and "seldom" and "never" were combined ("always/often" and "seldom/never"). The perceived availability of services was scored by the physicians as either being provided by the physicians themselves, readily available, or not readily available. The first two categories were combined as "readily available." To determine whether geographic variation influenced the reported patterns of care, the data were analyzed with regard to the region of the country in which the physician practiced (South, North Central, Northeast, or West). It was also possible to determine whether a physician practiced within a large metropolitan area (more than 1 million persons), a small metropolitan area (less than 1 million persons), or a nonmetropolitan area (area not included in a metropolitan statistical area).
Nonresponse-adjusted weighted data were used in the statistical
analyses.8 This was accomplished with the SUDAAN
software package (Research Triangle Institute).9 SUDAAN
analyses include estimates of basic statistical
parameters such as frequency distribution, means,
percentages, regression coefficients, test statistics
(
2, Fisher's F, and Student's
t tests), standard errors, and multinomial multiple logistic
regression analysisbased odds ratios that take into
account the complex nature of the sample design when estimating
variances.
| Results |
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Diagnostic Testing
Overall, 89% of physicians reported that they always or often
obtain a carotid ultrasound study in patients with recent (eg, within
the previous month) carotid-distribution TIA or completed minor
stroke. Cerebral angiography was reported as being always or often used
by 19% of physicians in these newly symptomatic patients.
Seventy percent of physicians responded that they always or often
obtain a carotid ultrasound study in asymptomatic
patients with a carotid bruit. In asymptomatic patients
without surgical contraindications, 13% of physicians reported that
they always or often obtain a cerebral angiogram if a carotid duplex
ultrasonography indicates 50% to 70% stenosis (Fig 1
, top). The proportion doing so increased to 33% if
the noninvasive test indicated >70% stenosis of the
extracranial CA (Fig 1
, middle). Approximately 42% of physicians who
reported that they had cerebral angiography readily available responded
that they seldom or never obtain the study in
asymptomatic patients with >70% CA stenosis
demonstrated by ultrasonography; this proportion increased to
approximately 67% if angiography was viewed as not readily available
(Fig 1
, middle; P=.005). The perceived availability of
cerebral angiography also influenced its reported use in newly
symptomatic patients. Forty-two percent of physicians
who viewed the test as being readily available responded that they
seldom or never use it for these patients, whereas 85% of those who
viewed cerebral angiography as not being readily available reported
that they seldom or never refer this type of patient for the procedure
(Fig 1
, bottom; P<.001).
|
Carotid Endarterectomy
The perceived availability of CE varies with physician specialty,
practice location, and region of the country.8 Multinomial
multiple logistic regression analysis was used to evaluate the
independent contributions of these variables and the clinical
characteristics of patients (eg, degree of stenosis and symptom
status) on the reported frequency of use (always or often versus
sometimes versus seldom or never) of CE (Table
). The
overall model was significant (P<.001). Symptom status, the
degree of stenosis, perceived availability of CE, and physician
specialty independently contributed to the explained variance in the
reported use of CE. The odds of performing CE were approximately four
times greater in patients with recent symptoms compared with
asymptomatic patients (P<.001). The odds of
performing the surgery were approximately four times greater in
patients with >70% stenosis compared with patients with 50%
to 70% stenosis (P<.001). Overall, noninternist
primary care physicians, internists, and neurologists were 50% to 60%
less likely to use CE than surgeons (P<.001). There were no
independent effects of practice location or region after the other
variables (eg, perceived availability) were considered.
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Fig 2
shows the impact of perceived availability of CE
on its reported frequency of use in four types of patients without
contraindications to surgery. For physicians perceiving CE as being
readily available, the reported frequency of use increases with both
the presence of recent symptoms and with increasing degrees of
stenosis (the procedure was reported as being always or often
recommended by 7% of physicians for asymptomatic
patients with 50% to 70% stenosis, by 26% for
asymptomatic patients with >70% stenosis, by
23% for newly symptomatic patients with 50% to 70%
stenosis, and by 60% for newly symptomatic
patients with >70% stenosis). The perceived availability of
CE influenced the reported frequency of its use for all groups of
patients except for those who were asymptomatic and who
had moderate-grade (50% to 70%) stenosis. This impact of
perceived availability is present even in newly
symptomatic patients with high-grade (>70%)
stenosis. If CE was perceived as being readily available, it
was reported as being seldom or never used by 15% of physicians; if
the procedure was viewed as not being readily available, it was
reported as being seldom or never used by 47% of physicians (Fig 2
,
bottom right).
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The multinomial multiple logistic regression analysis indicated
that the reported frequency of use of CE also varied by physician
specialty, independent of the effect of the perceived availability of
the procedure (Table
). Fig 3
compares the reported
frequency of use of CE according to physician specialty in the same
four types of patients without contraindications to surgery. There is
not a significant difference among the physician specialties in the
reported use of endarterectomy in
asymptomatic patients with moderate (50% to 70%)
degrees of stenosis of the extracranial CA (Fig 3
, top left;
P=.126). For asymptomatic patients with
higher degrees of stenosis, surgeons reported using CE more
frequently than it was recommended by other groups of physicians (Fig 3
, top right; P<.001). Similarly, surgeons responded that
they use CE more frequently than other groups of physicians for newly
symptomatic patients (TIA or minor stroke within the
previous month) with moderate ipsilateral CA stenosis (Fig 3
,
bottom left; P<.001). The reported use of CE also varied by
physician specialty for patients with recent TIA or minor stroke and
>70% stenosis of the ipsilateral CA (Fig 3
, bottom right;
P<.001). More than 80% of both surgeons and neurologists
responded that they always or often use CE for newly
symptomatic patients with high-grade CA
stenosis, whereas approximately 55% of noninternist primary
care physicians and internists reported that they would do so. About
47% of noninternist primary care physicians and 54% of internists
reported that they always or often refer this type of patient to a
neurologist. Approximately 23% of noninternist primary care
physicians, 16% of internists, 5% of neurologists, and 9% of
surgeons reported that they seldom or never use CE for patients with
high-grade CA stenosis and a TIA or minor stroke within the
previous month.
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| Discussion |
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Carotid duplex ultrasonography and cerebral angiography are important tests used in the evaluation of patients with cerebrovascular disease. In the setting of newly symptomatic patients, these tests may be used both as an aid in establishing the cause of the symptoms and as part of the presurgical evaluation of potential CE candidates. Carotid ultrasonography was reported as being readily available by 98% of surveyed physicians,8 and almost 90% of physicians reported that they always or often use the test in newly symptomatic patients. Only about 20% always or often obtain cerebral angiography in newly symptomatic patients, suggesting that this invasive test is being used selectively by practicing physicians.
In asymptomatic individuals, carotid duplex
ultrasonography is primarily used as a screening tool in candidates for
prophylactic CE. The subsequent use of conventional
angiography would be expected to vary with the degree of CA
stenosis revealed by the screening test. In fact, the
proportion of physicians reporting that they always or often obtain a
cerebral angiogram in asymptomatic patients increases
nearly threefold (13% to 33%) as the degree of stenosis
demonstrated by the noninvasive test increases from 50% to 70% to
>70%. In view of the fact that 70% of physicians reported that they
always or often obtain a carotid ultrasound study in patients with an
asymptomatic bruit, the reasons why this difference is
not greater are not entirely clear. Despite differences in opinion on
the advisability of performing CE solely on the basis of the results of
carotid ultrasonography,11 12 it is unlikely that most
physicians would proceed without conventional arteriography. Performing
a screening test but not acting on the result suggests that the test is
being used inappropriately. However, physicians were not asked whether
they would perform angiography if the carotid ultrasound indicated a
"critical" asymptomatic stenosis. It is
possible that physicians were using the screening test to identify this
subgroup. The perceived availability of a test may also influence the
frequency of its use, and cerebral angiography was viewed as relatively
unavailable by 12% of surveyed physicians.8 The reported
availability of cerebral angiography did not influence its use for
asymptomatic patients with moderate degrees of
stenosis (Fig 1
, top). In contrast, the frequency of use of
cerebral angiography in asymptomatic patients did vary
with the availability of the test if the ultrasound study indicated
higher-grade stenosis (Fig 1
, middle). Thus, part of the
disparity between the use of carotid ultrasonography as a screening
tool in asymptomatic patients and the reported
frequency of use of angiography if the ultrasound study indicated
high-grade stenosis may be due to the perceived
availability of angiography.
In accord with the data available at the time, the proportions of
physicians indicating that they would often or always recommend CE
varied with symptom status and degree of stenosis (Table
) and
were highest for newly symptomatic patients with
high-grade stenosis (Fig 2
, bottom right), intermediate in
the setting of symptomatic moderate-grade
stenosis (Fig 2
, bottom left) or asymptomatic
high-grade stenosis (Fig 2
, top right), and lowest for
asymptomatic moderate-grade stenosis (Fig 2
, top left). However, even in the group of patients most likely to
benefit from the surgery given the available data (those with newly
symptomatic high-grade stenosis), the perceived
availability of CE has a significant impact on its reported frequency
of use (Fig 2
, bottom right). After considering the impact of
perceived availability, there is no significant effect of practice
location or region of the country on the frequency of CE use (Table
).
However, CE was reported to be least available by physicians practicing
in the South and in nonmetropolitan settings.8 The reasons
for the perceived unavailability of CE to physicians practicing in the
South remain uncertain, but it is of particular importance because the
South represents the country's "stroke belt," with the
highest incidence of the disease.13 If the perceived
unavailability of CE to physicians practicing in the South is due to
actual unavailability, then the problem could be addressed through the
allocation of additional resources. If this is not the case, then the
problem could be addressed through clarification of referral mechanisms
and targeted provider education. Clarification and streamlining of
referral mechanisms might also partially address the perceived
unavailability of cerebral angiography and CE to physicians practicing
in nonmetropolitan areas.
The reported frequency of use of CE also varied by physician specialty
(Table
). The effect of physician specialty is independent of the
perceived availability of the procedure (Table
). The frequency of use
of CE was consistent with the data for diagnostic
testing and uniformly low across specialties for patients with
asymptomatic moderate-grade stenosis (Fig 3
, top left). In patients with newly symptomatic
high-grade stenosis, CE was reported as being always or
often used by more than 80% of neurologists and surgeons but only by
about half of internists and noninternist primary care physicians (Fig 3
, bottom right). Almost one in four noninternist primary care
physicians responded that they would seldom or never use CE for these
patients (Fig 3
, bottom right). It is possible that these groups of
physicians were not as aware of the findings of the randomized trials
that were available or had not yet incorporated the findings into their
practices. Possibly reflecting this uncertainty with regard to optimal
management strategies, about half of internists and noninternist
primary care physicians responded that they frequently consult
neurologists for this type of patient. Physicians in these specialties
are particularly important targets for educational efforts because they
are responsible for the majority of the care of patients at elevated
stroke risk.8
There were also significant differences by specialty in the use of CE
for patients with less clear indications for the surgery based on the
data available at the time of the survey. CE was used significantly
more frequently by surgeons than by other groups of physicians for
these patients (eg, asymptomatic patients with
high-grade stenosis [Fig 3
, top right] and
symptomatic patients with moderate-grade
stenosis [Fig 3
, bottom left]), possibly
representing a practice bias.
In summary, the perceived availability of cerebral angiography and CE influences their reported frequency of use by physicians, even for the group of patients most likely to benefit from the procedure. The reasons for this perceived unavailability are not apparent. The use of CE also varies with physician specialty training. The relative lack of use of CE for newly symptomatic patients with high-grade stenosis by noninternist primary care physicians and internists could be partially addressed through targeted educational efforts.
| Selected Abbreviations and Acronyms |
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| Acknowledgments |
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Received December 18, 1995; revision received January 25, 1996; accepted January 25, 1996.
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