USPSTF Against Asymptomatic Stenosis Screening

Adults without symptoms of carotid artery stenosis should not be screened with ultrasonography or other tests, according to a recommendation issued by the U.S. Preventive Services Task Force.

Carotid artery screening provides minimal benefit in asymptomatic adults, but the screening tests and treatments pose potential harm, judging from evidence reviewed by the U.S. Preventive Services Task Force (USPSTF).

"Available screening and confirmatory tests ... all have imperfect sensitivity and appreciable harms," the USPSTF advised in its recommendation. "Therefore, screening could lead to nonindicated surgeries that result in serious harms, including death, stroke, and myocardial infarction, in some patients."

The current USPSTF recommendation is based on reviews of the accuracy of screening tests, observational studies on screening and treatment of asymptomatic patients, and randomized controlled trials on treatment with carotid endarterectomy (Ann. Intern. Med. 2007;147:854-9).

The USPSTF review found that the usual method of screening for carotid artery stenosis--duplex ultrasonography--has moderate sensitivity and specificity and results in many false positives. For detecting carotid artery stenosis greater than 70%, the sensitivity is estimated to be 86%-90% and the specificity to be 87%-94%.

Results of ultrasonography are usually confirmed through digital subtraction angiography, but screening can cause serious adverse events of its own, according to the USPSTF review. For example, the task force estimated that if all positive ultrasounds were followed by digital subtraction angiography, about 1% of individuals would experience a nonfatal stroke as a result.

And those patients who bypass angiography and proceed with carotid endarterectomy are also at risk for stroke and other complications. A review of 14 observational studies that evaluated carotid endarterectomy complications in patients with asymptomatic carotid artery stenosis showed that 30-day perioperative stroke or death rates ranged from 1.6% to 3.7% overall.

While there is evidence of a reduced incidence of stroke for certain selected individuals with asymptomatic severe carotid artery stenosis who undergo carotid endarterectomy, the benefits are likely small in the general primary care population, the task force wrote in its recommendation.

Until more research is conducted on the potential benefits of carotid endarterectomy in the general population, the USPSTF urged physicians to focus on the medical management of risk factors for stroke.

This recommendation updates the USPSTF's 1996 review of screening for carotid artery stenosis. In 1996, the group found insufficient evidence to recommend for or against screening of asymptomatic patients through either physical exam or carotid ultrasonography.

The USPSTF is an independent body that makes recommendations on preventive care for asymptomatic patients. The group receives funding from the Agency for Healthcare Research and Quality, part of the U.S. Department of Health and Human Services.

The task force is not the only group that has examined the issue of carotid artery stenosis screening recently. In 2007, the American Society of Neuroimaging recommended consideration of screening of adults aged 65 or older with three or more cardiovascular risk factors. And the Society for Vascular Surgery has recommended ultrasonography screening for individuals aged 55 or older with certain cardiovascular risk factors.