U.S. Preventive Services Task Force Discourages Screening for Asymptomatic Carotid Artery Stenosis

The U.S. Preventive Services Task Force (USPSTF) , which reports recommendations to Congress, published new guidelines in the December 18th Annals of Internal Medicine regarding carotid artery screening in the asymptomatic public. In 1996, the same agency concluded that there was insufficient evidence to recommend for or against widespread screening for carotid artery stenosis (CAS). Following their most recent examination of this question, the USPSTF gave widespread screening of asymptomatic patients for CAS a “grade D” rating, which means in their opinion the potential harms outweigh the potential benefits.

The Task Force’s examination of systematic reviews, observational studies, and randomized controlled trails led to the three following observations:

• A relatively small proportion of all disabling, unheralded strokes are due to CAS.
• Noninvasive screening tests (duplex ultrasonography and magnetic resonance angiography) are prone to false-positive results, resulting in unnecessary treatment. Invasive screening by digital subtraction angiography can cause serious adverse events.
• The benefits of surgical treatment with carotid endarterectomy are judged to be no greater than small.

According to the authors, among adults without neurologic signs or symptoms, “it is not clear how to identify people whose risk for stroke is high enough to justify screening, yet who do not also have a high risk for surgical complications.” However, “if otherwise eligible, an individual who has a carotid-area transient ischemic attack should be evaluated promptly for consideration of carotid endarterectomy.”

The Society for Vascular Surgery (SVS) maintains in its Position Statement on Vascular Screenings that screening appropriately-selected high-risk groups of patients is in fact good medicine. An excerpt from the SVS statement:

Individuals 55 years of age or older with cardiovascular risk factors such as a history of hypertension, diabetes mellitus, smoking, hypercholesterolemia, or known cardiovascular disease may benefit from preventive screening for vascular disease. Ultrasound screenings have proven to be accurate in detecting vascular disease prior to active warning signs and before a major medical incident such as stoke or sudden death from aneurysm rupture. Appropriate screening examinations in high-risk individuals include:

• Ultrasound scan of the aorta to identify aortic aneurysms
• Ultrasound scan of the carotid arteries to assess stroke risk
• Blood pressure measurements in the legs to identify PAD and risk of heart disease

The SVS and the American Society of Neuroimaging (ASN) did submit comments to the USPSTF earlier this year, suggesting that age- and risk-appropriate populations might benefit from CAS screening.
The full text of these two USPSTF articles is available free from the Annals of Internal Medicine by clicking these links:

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

There is also an article in the same issue describing in detail the Task Force’s general methodology employed when determining recommendations:

• Update on the Methods of the U.S. Preventive Services Task Force: Estimating Certainty and Magnitude of Net Benefit