Approximately 10% of ischemic strokes are caused by carotid artery stenosis (CAS).
Estimated prevalence of asymptomatic CAS is 1%.
The specificity of ultrasonography ranges from 88% to 94% for CAS of ≥50% to ≥70%).
Ultrasonography use in low-prevalence populations yields many false-positive results.
Current evidence does not establish overall benefit of carotid endarterectomy, stenting, or intensification of medical therapy with CAS ultrasound screening.
Potential for overall benefit of US screening is limited by low prevalence and harms.
USPSTF: recommends not to screen the general population for carotid stenosis
Reviews and meta-analyses demonstrate no studies providing information suggesting screening for carotid stenosis reduces stroke.
With the specificity of 92% carotid ultrasound screening leads to many more false positive results than true positive results given the low prevalence of asymptomatic carotid stenosis.
Common noninvasive ways to screen for carotid stenosis include: duplex ultrasound, CT angiogram and MR angiography.
In carotid ultrasound, the degree of carotid stenosis is determined in large degree by measuring the velocity of blood flow at various segments of the artery.
A peak systolic velocity 200 CM/S or greater on ultrasound has a sensitivity of 90% and specificity of 94% for diagnosing angiographic stenosis of 70%.
Ultrasound measurements can be affected by heavy calcification of the artery and contours of the neck.