Screening for asymptomatic carotid artery stenosis could bring more harm than benefit

CHAPEL HILL, N.C. — Researchers from UNC-Chapel Hill and RTI International conducted an evidence review that was used by the U.S. Preventive Services Task Force (USPSTF), a task force of national medical experts, to recommend against screening for asymptomatic carotid artery stenosis in adults.

Carotid artery stenosis (CAS) is the narrowing of arteries in the head and neck and leads to about 10 percent of ischemic strokes, which are those created by blood clots. About 1 of 100 U.S. adults have asymptomatic CAS. Screening procedures, such as ultrasound, are widely available, and free or out-of-pocket cash screenings are offered in public locations across the country.

Researchers from the RTI International-UNC Evidence-based Practice Center (EPC) reviewed published data to determine whether screening adults with no symptoms of CAS reduces the risk of stroke. The evidence review was commissioned by the USPSTF, an independent panel of experts in preventive health that makes recommendations about health screenings and preventive services. 

After reviewing the findings, the USPSTF recommended against screening for asymptomatic CAS in the general adult population. The recommendation and journal article were published in the July 8 issue of Annals of Internal Medicine. 

Daniel Jonas, lead author of the study and professor in the UNC department of medicine and the Cecil G. Sheps Center for Health Services Research, said the evidence review found more potential harms than benefit from screening.

"Using ultrasound to screen for asymptomatic carotid artery stenosis in the general population would yield many false-positive results, leading to unnecessary interventions and harm," Jonas said. "The rate of stroke or death after surgery for carotid artery stenosis in clinical trials was 2.4 percent. It was 3.3 percent in observational studies. The potential for overall population benefit of screening for and treating asymptomatic carotid artery stenosis is limited by low prevalence and harms."

The research team also found a lack of externally validated and reliable tools to determine who is more likely to have CAS.  In addition, Jonas said that improved medical therapy has led to reduced occurrence of the strokes that surgery or stenting could potentially prevent, making it more likely that the harms from procedures would outweigh the benefits.

The researchers also stated that the review was specifically for adults who did not have symptoms of CAS, and suggested that patients who have symptoms (e.g., vision loss, weakness, slurred speech) should call 911 or consult their doctor immediately for emergency treatment.

The RTI-UNC EPC is a collaboration between RTI International and the University of North Carolina at Chapel Hill funded by the Agency for Healthcare Research and Quality. Jonas co-directs the EPC with Meera Viswanathan, Ph.D., health services researcher at RTI.