Screening for Carotid Artery Stenosis: An Update of the Evidence for the U.S. Preventive Services Task Force

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.