Recommendation Statement
U.S. Preventive Services Task Force (USPSTF)
- The U.S. Preventive Services
Task Force (USPSTF) makes recommendations about preventive care services
for patients without recognized signs or symptoms of the target condition.
- It bases its recommendations
on a systematic review of the evidence of the benefits and harms and an
assessment of the net benefit of the service.
- The USPSTF recognizes that
clinical or policy decisions involve more considerations than this body of
evidence alone. Clinicians and policymakers should understand the evidence
but individualize decisionmaking to the specific patient or situation.
Select for copyright and source information.
Contents
Summary of Recommendations and Evidence
Clinical Considerations
Discussion
Recommendations of Others
References
Members of the USPSTF
Summary of Recommendations and Evidence
- The
USPSTF recommends against screening for asymptomatic carotid artery stenosis
(CAS) in the general adult population. (This is a grade "D" recommendation)
|
Go to
Table 1 for a description of the USPSTF grades and Table 2 for a description of
the USPSTF classification of levels of certainty regarding net benefit.
Rationale:
Importance. Good evidence indicates that although stroke is a
leading cause of death and disability in the United States, a relatively small
proportion of all disabling, unheralded strokes is due to CAS.
Detection. The most feasible screening test for
severe CAS (for example, 60% to 99% stenosis) is duplex ultrasonography. Good
evidence indicates that this test has moderate sensitivity and specificity and
yields many false-positive results. A positive result on duplex ultrasonography
is often confirmed by digital subtraction angiography, which is more accurate
but can cause serious adverse events. Noninvasive confirmatory tests, such as magnetic
resonance angiography, involve some inaccuracy. Given these facts, some people
with false-positive test results may receive unnecessary invasive carotid
endarterectomy surgery.
Benefits
of Detection and Early Intervention. Good
evidence indicates that in selected, high-risk trial participants with
asymptomatic severe CAS, carotid endarterectomy by selected surgeons reduces
the 5-year absolute incidence of all strokes or perioperative death by
approximately 5%. These benefits would be less among asymptomatic people in the
general population. For the general primary care population, the benefits are
judged to be no greater than small.
Harms
of Detection and Early Intervention. Good evidence indicates that both the testing strategy and the treatment with carotid
endarterectomy can cause harms. A testing strategy that includes angiography
will itself cause some strokes. A testing strategy that does not include
angiography will cause some strokes by leading to carotid endarterectomy in
people who do not have severe CAS. In excellent centers, carotid endarterectomy
is associated with a 30-day stroke or mortality rate of about 3%; some areas
have higher rates. These harms are judged to be no less than small.
USPSTF Assessment. The USPSTF concludes that for individuals with
asymptomatic CAS there is moderate certainty that the benefits of screening do
not outweigh the harms ("D" recommendation).
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Clinical Considerations
Patient
Population
This
recommendation applies to adults without neurologic signs or symptoms,
including a history of transient ischemic attacks or stroke. If otherwise
eligible, an individual who has a carotid-area transient ischemic attack should
be evaluated promptly for consideration of carotid endarterectomy.
Risk Assessment
In
a setting of excellent surgical care and low complication rates, screening may
benefit patients who have a very high risk for stroke. It is not clear,
however, how to identify people whose risk for stroke is high enough to justify
screening, yet do not also have a high risk for surgical complications. The
major risk factors for CAS include older age, male sex, hypertension, smoking,
hypercholesterolemia, and heart disease.
Screening
Tests
Available
screening and confirmatory tests (duplex ultrasonography, digital subtraction
angiography, and magnetic resonance angiography) all have imperfect sensitivity
and appreciable harms. Therefore, screening could lead to non-indicated
surgeries that result in serious harms, including death, stroke, and myocardial
infarction, in some patients.
Useful
Resources
In
other recommendations, the USPSTF notes that adults should be screened for
hypertension, hyperlipidemia, and smoking. In addition, clinicians should
discuss aspirin chemoprevention for those who have an increased risk for
cardiovascular disease. The evidence and recommendations on these conditions
from the USPSTF are available on the Agency for Healthcare Research and Quality
Web site at www.preventiveservices.ahrq.gov.
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Discussion
Burden
of Disease
The
contribution of CAS 60% to 99% to the morbidity and mortality associated with
stroke, or to the natural progression of asymptomatic CAS in the general
population, is not precisely known.1,2 Based on population-based
studies and the accuracy of carotid duplex, the estimated prevalence of CAS 60%
to 99% in the general population over age 65 years is about 1%. Studies have
found that CAS is more prevalent in older adults, smokers, those with
hypertension, and those with heart disease. Research has not found any single
risk factor or clinically useful risk stratification tool that can reliably and
accurately distinguish people who have clinically important CAS from those who
do not.
Scope
of Review
In
1996, the USPSTF concluded that evidence was insufficient to recommend for or
against screening of asymptomatic patients for CAS by using a physical examination
or carotid ultrasonography. To update its recommendation, the USPSTF examined
high-quality evidence on the natural history of CAS, systematic reviews of the
accuracy of screening tests, and randomized, controlled trials (RCTs) of the
benefits of treatment of CAS with carotid endarterectomy. Because the magnitude
of potential surgical harms is such an important consideration in the treatment
of CAS, the USPSTF conducted a systematic review of this issue.
Accuracy
of Screening Tests
Two
meta-analyses provide information on the accuracy of carotid duplex ultrasonography
in detecting clinically important stenosis. Recent systematic reviews of
studies about the accuracy of carotid duplex ultrasonography, by using digital
subtraction angiography as the reference standard, estimated the sensitivity to
be 86% to 90% and the specificity to be 87% to 94% for detecting CAS greater
than 70%.3,4 The estimated sensitivity and specificity of
carotid duplex ultrasonography to detect CAS of 60% or more are approximately
94% and 92%, respectively.3 The reliability of carotid duplex ultrasonography
is not established.3 One meta-analysis noted that the measurement
properties used among various ultrasonography laboratories varied greatly and
to a clinically important degree.3 In 1996, the USPSTF reviewed
the evidence for screening for bruits on physical examination and found that
the test had poor reliability and poor sensitivity.5
Effectiveness
of Early Detection and Treatment
Two
good-quality RCTs, the ACAS (Asymptomatic Carotid Atherosclerosis Study) and
the ACST (Asymptomatic Carotid Surgery Trial), compared carotid endarterectomy plus
medical management to medical management alone in participants without symptoms
attributable to the studied artery.6,7 The ACAS projected a
5-year rate of ipsilateral stroke and any perioperative stroke or death that
was lower in the carotid endarterectomy group than in the medical group: 5.1%
versus 11.0% (relative risk reduction, 0.53 [95% CI, 0.22% to 0.72%]). If
strokes associated with angiography were included, the difference between the groups
was 5.6% versus 11.0%, or an absolute difference of 5.4 percentage points over
5 years. The estimated relative risk reduction was greater for men than for
women (0.66 and 0.17, respectively). The ACST projected a lower 5-year rate of
any stroke or perioperative death in the carotid endarterectomy group than in
the medical group: 6.4% versus 11.8% (absolute difference, 5.4 percentage
points [CI 2.96% to 7.75%]). About half of the strokes prevented by carotid
endarterectomy were disabling. The treatment groups did not statistically
significantly differ in all-cause mortality in either of the studies.
The
RCTs on carotid endarterectomy for asymptomatic CAS have important limitations
in terms of their generalizability to the primary care population. The RCTs included
highly selected participants and surgeons. The 30-day perioperative results of
the RCTs were reported as a combined outcome that did not include acute
nonfatal myocardial infarction, which is an important complication. The medical
treatment arm in the RCTs was poorly defined, was not kept constant over the
course of the study, and would not have included treatments that are now
considered to be optimal medical management, including aggressive management of
blood pressure and lipids.
Potential
Harms of Screening and Treatment
Tests
done to confirm carotid duplex ultrasonography have associated harms. If all
positive tests are followed by digital subtraction angiography, about 1% of
people would experience a nonfatal stroke as a result of the angiogram. If
positive tests are not followed by confirmatory angiography but rather by
magnetic resonance angiography or computed tomography angiography—tests with
less than 100% accuracy—some patients will have unnecessary carotid
endarterectomy, with consequent harms in the absence of proven benefit.
Fourteen
good- or fair-quality observational studies that evaluated carotid
endarterectomy complications in patients with asymptomatic CAS were identified
for USPSTF review. Overall, 30-day perioperative stroke or death rates in
asymptomatic patients ranged from 1.6% to 3.7%.2 Participants in
ACAS had a perioperative rate of stroke or death of 2.7% overall (1.7% for men
and 3.6% for women). In ACST, the perioperative rate of stroke or death was
3.1% overall but was higher for women (3.7%) than for men (2.4%). The
observational studies reporting perioperative nonfatal myocardial infarctions
showed a rate of approximately 0.7% to 1.1%8-10 Patients with
more comorbid conditions had a rate of nonfatal myocardial infarction up
to 3.3%.9 The rate of nonfatal perioperative myocardial
infarction reported for the surgical group in the RCTs varied from 0.6% to
1.9%. Two Medicare-based studies found variation in perioperative stroke and
death among 10 states.11,12 In the first study, the statewide
rates ranged from 2.3% to 6.7%; a follow-up study for the same 10 states found
similar results as in 2001, with rates ranging from 1.4% to 6.0%.
Estimate
of the Magnitude of Net Benefit
In
patients and surgeons similar to those in the RCTs, treatment with carotid
endarterectomy for asymptomatic CAS can result in a net absolute reduction in
stroke rates—approximately 5% over 5 to 6 years (about 2.5% absolute risk
reduction for disabling strokes). The number needed to treat for 5 years to
prevent 1 stroke is about 20 (number needed to treat to prevent 1 disabling
stroke is about 40). This benefit has been shown in selected patients with
selected surgeons, and must be weighed against a small increase in nonfatal myocardial
infarctions. The net benefit for carotid endarterectomy largely depends on
people surviving the perioperative period without complications and living for 5
years. The 2 RCTs that found a benefit to surgery compared with medical
management had 30-day perioperative rates of stroke and death of 2.7% to 3.1%
and some large observational studies have shown higher rates.
If
ultrasonography screening were followed by magnetic resonance angiography confirmation,
about 23 strokes would be prevented over 5 years by screening 100,000 people
with a prevalence of CAS of 1%. Thus, about 4,348 people would need to
undergo screening to prevent 1 stroke (number needed to screen) after 5 years. Twice
this number (8,696) would need to be screened to prevent 1 disabling stroke.
How
Does the Evidence Fit with Biological Understanding?
The
medical treatment group in the RCTs was poorly defined and probably did not
include intensive blood pressure and lipid control, which is standard practice
today. It is difficult to determine what effect current standard medical
therapy would have on overall benefit from carotid endarterectomy. The Kaplan–Meier
curves in ACST cross from net harm to net benefit at about 1.5 years after carotid
endarterectomy for men and at nearly 3 years after carotid endarterectomy for
women13-17 The average follow-up time in ACAS and ACST was 2.7 and 3.4
years, respectively; the estimated survival beyond the actual follow-up time
may not be applicable in this situation. It is possible that the benefit from carotid
endarterectomy is limited to a specific interval and does not continue unabated
into the future. Thus, the actual (not projected) risk reduction for carotid
endarterectomy over 5 to 10 years is still uncertain.
Although
this report did not review the evidence on medical treatment, accepted medical
strategies to prevent stroke are available. Until research addresses the gaps
in the evidence that screening and treatment with carotid endarterectomy provides
overall benefits to the general population, clinicians' efforts might be more
practically focused on optimizing medical management of risk factors of stroke.
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Recommendations of Others
In
2006, the American Heart Association/American Stroke Association did not
recommend screening the general population for asymptomatic carotid stenosis.18 The American Society of Neuroimaging released recommendations in 2007
that also recommended against screening in unselected populations, but advised
that screening of adults age 65 years or older with 3 or more cardiovascular
risk factors should be considered.19 In 2007, the Society for
Vascular Surgery recommended ultrasonography screening for individuals age 55
years or older with cardiovascular risk factors, such as a history of
hypertension, diabetes mellitus, smoking, hypercholesterolemia, or known
cardiovascular disease.20
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References
1. Wolff T, Guirguis-Blake J, Miller T, Gillespie M, Harris R. Screening
for asymptomatic carotid artery stenosis. Evidence Synthesis No. 50. AHRQ
Publication No. 08-05102-EF-1. Rockville, MD: Agency for Healthcare Research
and Quality; December 2007.
2. Wolff T, Guirguis-Blake J, Miller T, Gillespie M, Harris R. Screening
for carotid artery stenosis: an update of the evidence for the U.S. Preventive
Services Task Force. Ann Intern Med 2007;147:860-70.
3. Jahromi AS, Cinà CS, Liu Y, Clase CM. Sensitivity and specificity of
color duplex ultrasound measurement in the estimation of internal carotid
artery stenosis: a systematic review and meta-analysis. J Vasc Surg
2005;41:962-72. [PMID: 15944595]
4. Nederkoorn PJ, van der Graaf Y, Hunink MG. Duplex ultrasound and
magnetic resonance angiography compared with digital subtraction angiography in
carotid artery stenosis: a systematic review. Stroke 2003;34:1324-32. [PMID:
12690221]
5. Guide to Clinical Preventive Services, 2nd Edition: U.S. Preventive Services
Task Force; 1996.
6. Endarterectomy for asymptomatic carotid artery stenosis. Executive
Committee for the Asymptomatic Carotid Atherosclerosis Study. JAMA 1995;273:1421-8.
[PMID: 7723155]
7. Halliday A, Mansfield A, Marro J, Peto C, Peto R, Potter J, et al.; MRC
Asymptomatic Carotid Surgery Trial (ACST) Collaborative Group. Prevention
of disabling and fatal strokes by successful carotid endarterectomy in patients
without recent neurological symptoms: randomised controlled trial. Lancet
2004;363:1491-502. [PMID: 15135594]
8. Horner RD, Oddone EZ,
Stechuchak KM, Grambow SC, Gray J, Khuri SF, et al. Racial variations in postoperative outcomes of
carotid endarterectomy: evidence from the Veterans Affairs National Surgical
Quality Improvement Program. Med Care 2002;40:I35-43. [PMID: 11789630]
9. Halm EA, Chassin MR, Tuhrim S, Hollier LH, Popp AJ, Ascher E, et al. Revisiting the appropriateness of carotid endarterectomy. Stroke
2003;34:1464-71. [PMID: 12738896]
10. Karp HR, Flanders WD, Shipp CC, Taylor B, Martin D. Carotid
endarterectomy among Medicare beneficiaries: a statewide evaluation of
appropriateness and outcome. Stroke 1998;29:46-52. [PMID: 9445327]
11. Kresowik TF, Bratzler D, Karp HR, Hemann RA, Hendel ME, Grund SL, et al. Multistate utilization, processes, and outcomes of carotid endarterectomy. J
Vasc Surg 2001;33:227-34; discussion 234-5. [PMID: 11174772]
12. Kresowik TF, Bratzler DW, Kresowik RA, Hendel ME, Grund SL, Brown KR, et al. Multistate improvement in process and outcomes of carotid endarterectomy. J
Vasc Surg 2004;39:372-80. [PMID: 14743139]
13. Finsterer J, Stöllberger C. ACST: which subgroups will benefit most from
carotid endarterectomy? [Letter]. Lancet 2004;364:1124; author reply 1125-6.
[PMID: 15451214]
14. Kietselaer BL, Hofstra L, Narula J. ACST: which subgroups will benefit
most from carotid endarterectomy? [Letter]. Lancet 2004;364:1124-5; author
reply 1125-6. [PMID: 15451215]
15. Kumar S, Sinha B. ACST: which subgroups will benefit most from carotid
endarterectomy? [Letter]. Lancet 2004;364:1125; author reply 1125-6. [PMID:
15451217]
16. Masuhr F, Busch M. ACST: Which subgroups will benefit most from carotid
endarterectomy? [Letter]. Lancet 2004;364:1123-4; author reply 1125-6. [PMID:
15451213]
17. Rothwell PM. ACST: Which subgroups will benefit most from carotid
endarterectomy? [Letter]. Lancet 2004;364:1122-3; author reply 1125-6. [PMID:
15451212]
18. Goldstein LB, Adams R, Alberts MJ, Appel LJ, Brass LM, Bushnell CD, et al.; American Heart Association/American Stroke Association Stroke Council. Primary prevention of ischemic stroke: a guideline from the American Heart
Association/American Stroke Association Stroke Council: cosponsored by the
Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group;
Cardiovascular Nursing Council; Clinical Cardiology Council; Nutrition,
Physical Activity, and Metabolism Council; and the Quality of Care and Outcomes
Research Interdisciplinary Working Group: the American Academy of Neurology
affirms the value of this guideline. Stroke 2006;37:1583-633. [PMID: 16675728]
19. Qureshi AI, Alexandrov AV, Tegeler CH, Hobson RW II, Dennis Baker J, Hopkins
LN; American Society of Neuroimaging. Guidelines for screening of
extracranial carotid artery disease: a statement for healthcare professionals
from the multidisciplinary practice guidelines committee of the American
Society of Neuroimaging; cosponsored by the Society of Vascular and Interventional
Neurology. J Neuroimaging 2007;17:19-47. [PMID: 17238868]
20. Society for Vascular Surgery. SVS Position Statement on Vascular
Screenings, 2007. Accessed at http://www.vascularweb.org/_CONTRIBUTION_PAGES/Patient_Information/screenings/SVS_Position_Statement_on_Vascular_Screenings.html
on 11 May 2007.
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Members of the U.S. Preventive Services Task Force*
Members
of the U.S. Preventive Services Task Force are Ned Calonge, MD, MPH, Chair,
USPSTF (Chief Medical Officer and State Epidemiologist, Colorado Department of
Public Health and Environment, Denver, Colorado); Diana B. Petitti, MD, MPH ,
Vice-chair, USPSTF (Department of Preventive Medicine, Keck School of Medicine,
University of Southern California, Sierra Madre, California); Thomas G. DeWitt,
MD (Carl Weihl Professor of Pediatrics and Director of the Division of General
and Community Pediatrics, Department of Pediatrics, Children’s Hospital Medical
Center, Cincinnati, Ohio); Leon Gordis, MD, MPH, DrPH (Professor, Epidemiology
Department, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland);
Kimberly D. Gregory, MD, MPH (Director, Women’s Health Services Research and
Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Cedars-Sinai
Medical Center, Los Angeles, California); Russell Harris, MD, MPH (Professor of
Medicine, Sheps Center for Health Services Research, University of North
Carolina School of Medicine, Chapel Hill, North Carolina); Kenneth W. Kizer,
MD, MPH (President and CEO, National Quality Forum, Washington, DC); Michael L.
LeFevre, MD, MSPH (Professor, Department of Family and Community Medicine,
University of Missouri School of Medicine, Columbia, Missouri); Carol
Loveland-Cherry, PhD, RN (Executive Associate Dean, Office of Academic Affairs,
University of Michigan School of Nursing, Ann Arbor, Michigan); Lucy N. Marion,
PhD, RN (Dean and Professor, School of Nursing, Medical College of Georgia,
Augusta, Georgia); Virginia A. Moyer, MD, MPH (Professor, Department of
Pediatrics, University of Texas Health Science Center, Houston, Texas); Judith
K. Ockene, PhD (Professor of Medicine and Chief of Division of Preventive and
Behavioral Medicine, University of Massachusetts Medical School, Worcester, Massachusetts);
George F. Sawaya, MD (Associate Professor, Department of Obstetrics,
Gynecology, and Reproductive Sciences and Department of Epidemiology and
Biostatistics, University of California, San Francisco, California); Albert L.
Siu, MD, MSPH (Professor and Chairman, Brookdale Department of Geriatrics and
Adult Development, Mount Sinai Medical Center, New York, New York); Steven M.
Teutsch, MD, MPH (Executive Director, Outcomes Research and Management, Merck
& Company, Inc., West Point, Pennsylvania);** and Barbara P. Yawn, MD, MSPH, MSc (Department of Research, Olmsted Medical Center, Rochester, MN).
*Members of the Task Force at the time this recommendation was finalized. For a list of current Task Force members, go to http://www.ahrq.gov/clinic/uspstfab.htm.
**Dr. Teutsch was recused from the discussion and vote
on this issue.
Disclaimer: Recommendations made by the USPSTF are independent of
the U.S. government. They should not be construed as an official position
of the Agency for Healthcare Research and Quality or the U.S.
Department of Health and Human Services.
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Copyright and Source Information
This document is in the public domain within the United States. For
information on reprinting, contact Randie Siegel, Director, Division of
Printing and Electronic Publishing, Agency for Healthcare Research and Quality,
540 Gaither Road, Rockville, MD 20850.
Requests for linking or to incorporate content in electronic resources
should be sent to: info@ahrq.gov.
Source: U.S. Preventive Services Task Force. Screening for carotid artery stenosis: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2007;147:854-859..
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AHRQ Publication No. 08-05102-EF-2
Current as of December 2007
Internet Citation:
U.S. Preventive Services Task Force. Screening for Carotid Artery Stenosis: U.S. Preventive Services Task Force Recommendation Statement. AHRQ Publication No. 08-05102-EF-2, December 2007. First published in Ann Intern Med 2007;147:854-859. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/uspstf07/cas/casrs.htm