Screening for carotid artery stenosis: an update of the evidence for the U.S. Preventive Services Task Force
Tracy Wolff1, Janelle Guirguis-Blake, Therese Miller
1Center for Primary Care, Prevention, and Clinical Partnerships, Agency for Healthcare Research and Quality, Rockville, Maryland 20850, USA.
Insights
Screening for asymptomatic carotid artery stenosis (CAS) lacks direct evidence of stroke reduction. While ultrasonography is accurate, the benefits of surgical treatment are uncertain due to potential harms and low prevalence of treatable disease.
Area of Science:
- Cerebrovascular disease research
- Diagnostic accuracy of medical screening
- Interventional cardiology and surgery outcomes
Background:
- Cerebrovascular disease is a leading cause of death in the US.
- Asymptomatic carotid artery stenosis (CAS) accounts for a small proportion of all strokes.
- Previous guidelines found insufficient evidence to recommend CAS screening.
Purpose of the Study:
- To evaluate the benefits and harms of screening for asymptomatic CAS using duplex ultrasonography.
- To assess the effectiveness of carotid endarterectomy (CEA) treatment for CAS.
Main Methods:
- Systematic review of randomized controlled trials (RCTs) and observational studies (1994-2007).
- Searched MEDLINE, Cochrane Library, and expert recommendations.
- Assessed evidence on screening accuracy, stroke reduction, and treatment-related morbidity/mortality.
Main Results:
- No RCTs directly evaluated screening for CAS.
- Ultrasonography demonstrates high accuracy: 94% sensitivity and 92% specificity.
- CEA may reduce strokes by ~5% over 5 years in selected patients, but carries a 2.7%-6.7% risk of stroke or death.
Conclusions:
- Evidence is insufficient to stratify individuals by risk for clinically significant CAS.
- The net stroke reduction from screening and CEA in the general asymptomatic population is unknown.
- Benefits of CEA are limited by low prevalence of treatable disease and treatment-related harms.
Background:
Cerebrovascular disease is the third leading cause of death in the United States. The proportion of all strokes attributable to previously asymptomatic carotid artery stenosis (CAS) is low. In 1996, the U.S. Preventive Services Task Force concluded that evidence was insufficient to recommend for or against screening of asymptomatic persons for CAS by using physical examination or carotid ultrasonography.
Purpose:
To examine the evidence of benefits and harms of screening asymptomatic patients with duplex ultrasonography and treatment with carotid endarterectomy for CAS.
Data Sources:
MEDLINE and Cochrane Library (search dates January 1994 to April 2007), recent systematic reviews, reference lists of retrieved articles, and suggestions from experts.
Study Selection:
English-language randomized, controlled trials (RCTs) of screening for CAS; RCTs of carotid endarterectomy versus medical treatment; systematic reviews of screening tests; and observational studies of harms from carotid endarterectomy were selected to answer the following questions: Is there direct evidence that screening with ultrasonography for asymptomatic CAS reduces strokes? What is the accuracy of ultrasonography to detect CAS? Does intervention with carotid endarterectomy reduce morbidity or mortality? Does screening or carotid endarterectomy result in harm?
Data Extraction:
All studies were reviewed, abstracted, and rated for quality by using predefined Task Force criteria.
Data Synthesis:
No RCTs of screening for CAS have been done. According to systematic reviews, the sensitivity of ultrasonography is approximately 94% and the specificity is approximately 92%. Treatment of CAS in selected patients by selected surgeons could lead to an approximately 5-percentage point absolute reduction in strokes over 5 years. Thirty-day stroke and death rates from carotid endarterectomy vary from 2.7% to 4.7% in RCTs; higher rates have been reported in observational studies (up to 6.7%).
Limitations:
Evidence is inadequate to stratify people into categories of risk for clinically important CAS. The RCTs of carotid endarterectomy versus medical treatment were conducted in selected populations with selected surgeons.
Conclusion:
The actual stroke reduction from screening asymptomatic patients and treatment with carotid endarterectomy is unknown; the benefit is limited by a low overall prevalence of treatable disease in the general asymptomatic population and harms from treatment.
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