No Screening of Asymptomatic Carotid Artery Stenosis in General Population, Says USPSTF

Michael O'Riordan
December 20, 2007 — The US Preventive Services Task Force (USPSTF) has issued new clinical guidelines regarding the use of screening for asymptomatic carotid artery stenosis (CAS) and concludes with "moderate certainty" that the benefits of screening do not outweigh the risks [1]. With this, the task force concludes that asymptomatic individuals in the general population should not be routinely screened for CAS.
The class D recommendation of the USPSTF is now published in the December 18, 2007 issue of the Annals of Internal Medicine and is based on a review of the evidence by Dr Tracy Wolff (Agency for Healthcare Research and Quality, Rockville, MD) and colleagues [2].
The last guidelines were published in 1996, with the task force concluding then that the evidence was insufficient to recommend for or against screening of asymptomatic patients for CAS by physical examination or carotid ultrasonography. To update this recommendation, the USPSTF examined evidence on the natural history of carotid stenosis and reviewed the accuracy of the screening tests, as well as reviewing clinical-trial evidence of the benefits of treating CAS with carotid endarterectomy.
Regarding screening, the task force writes that while duplex ultrasonography is the most feasible test, it has only moderate sensitivity and specificity and yields many false-positive results. Positive results are usually confirmed by angiography, which is more accurate but also poses risks of serious adverse events. Noninvasive confirmation tests, such as magnetic resonance imaging (MRI), can also be inaccurate.
"Given these facts, some people with false-positive test results may receive unnecessary invasive carotid endarterectomy surgery," according to the USPSTF.
In terms of detection and early intervention, the task force notes that good evidence — from the Asymptomatic Carotid Atherosclerosis Study (ACAS) and the Asymptomatic Carotid Surgery Trial (ACST) — has shown that in high-risk subjects with asymptomatic, severe CAS, carotid endarterectomy by selected surgeons reduces the five-year absolute incidence of all strokes or perioperative death by 5%. However, these benefits, they write, would be less among the general population, and for the general primary-care patient, "the benefits are judged to be no greater than small."
The USPSTF report did not review the evidence on medical treatment but notes that accepted medical strategies to prevent stroke are available.
"Until research addresses the gaps in the evidence that screening and treatment with carotid endarterectomy provides overall benefits to the general population, clinicians' efforts might be more practically focused on optimizing medical management of risk factors of stroke," concludes the USPSTF.

Sources
US Preventive Services Task Force. Screening for carotid stenosis: US Preventive Services Task Force Recommendation Statement. Ann Intern Med 2007; 147: 854-859.
Wolff T, Guirguis-Blake J, Miller T, et al. Screening for carotid stenosis: An update of the evidence for the US Preventive Services Task Force. Ann Intern Med 2007; 147: 860-870.