USPSTF Recommends Against Screening For Asymptomatic Carotid Artery Stenosis

Although stroke is a leading cause of death and disability in the United States, a relatively small proportion of all disabling strokes are due to Carotid Artery Stenosis (CAS).

The most commonly used screening test for severe CAS (60% to 99% stenosis) is duplex ultrasonography.  The accuracy of carotid duplex ultrasonography, by using digital subtraction angiography as the reference standard, estimate the sensitivity to be 86% to 90% and the specificity to be 87% to 94% for detecting CAS greater than 70%. The estimated sensitivity and specificity of carotid duplex ultrasonography to detect CAS of 60% or more are approximately 94% and 92%, respectively.  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.  Good evidence indicates that duplex ultrasonography has moderate sensitivity and specificity but yields many false-positive results. A positive result on duplex ultrasonography is often confirmed by digital subtraction angiography, which is more accurate but is associated with complications. Given these facts, some people with a false-positive test results may receive unnecessary carotid endarterectomy surgery.

The evidence analyzed by the U.S. Preventive Services Task Force (USPSTF) indicates that in selected, high-risk trial participants with asymptomatic severe CAS, carotid endarterectomy by select surgeons reduces the 5-year absolute incidence of all strokes or peri-operative 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.

Therefore 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.

The U.S. Preventive Services Task Force concludes that for individuals with asymptomatic CAS there is moderate certainty that the benefits of screening do not outweigh the harms and its draft document gives a “D” recommendation.