Panel Says Most Carotid Screening Is Unnecessary
The U.S. Preventive Services Task Force has targeted another common screening test as being overused and too often resulting in inappropriately aggressive follow-up care. This one involves taking ultrasound pictures of the arteries in the neck.
This time, as explained on MedPageToday.com, the task force reaffirmed its original recommendation in 2007 that adults who don’t show symptoms of narrowed carotid arteries should not be screened for the disorder.
After reviewing the latest evidence, the USPSTF concluded "with moderate certainty that the harms of screening for asymptomatic carotid artery stenosis outweigh the benefits."
Humans have two carotid arteries, running up either side of the neck. They are the major highways delivering blood to the brain. Narrowed carotid arteries increase the risk of stroke, but nobody yet knows really good ways to cut that risk or figure out who is at the highest risk.
Screening generally is done by duplex ultrasonography, which combines traditional ultrasound with Doppler ultrasound. The first uses sound waves bouncing off blood vessels to render an image, and the second uses sound waves reflecting off of something that moves, such as blood, to measure speed and define the flow characteristics.
Duplex ultrasonography, says MedPageToday, is relatively accurate, but like most diagnostic tests, it can render false positives, and that means additional testing. And like all diagnostic tests, it can miss some cases of stenosis.
Targeting only some people for the screening is tough because there are no widely accepted criteria for who’s at the greatest risk for having carotid stenosis.
Joining the USPSTF in accepting that routine screening isn't a good idea are the American Heart Association/American Stroke Association and the American College of Cardiology.
Studies indicate that the incidence of carotid artery stenosis is low in the general population, maybe even fewer than 1 in 100 people. When stenosis is present, it seldom causes a stroke, and there are no reliable ways to tell which cases might carry that risk, and which don’t.
If carotid stenosis is confirmed, the risk-benefit trade-off of the possible interventions isn’t great. One intervention, endarterectomy, is the surgical removal of the lining of an artery, along with any obstructive deposits. Another intervention, stenting, is the insertion of a tube to hold a constricted artery open.
According to MedPageToday, trials of patients with asymptomatic carotid stenosis have shown that endarterectomy cuts the risk of stroke or perioperative death (death within a couple weeks of surgery) by 3.5 in 100, versus with medical therapy (drugs, for example). But those trials were done when medical therapy was not as good as it is now, say medical professionals, who peg the risk of stroke with at about 1 in 100, or lower, if you get the best medical therapy.
Stenting, too, shows no meaningful benefit over good medical therapy.
If your response to carotid stenosis is more intense medical therapy, there’s no evidence that’s beneficial either, according to the task force. So any potential benefits to screening for detecting and treating carotid stenosis are likely to be small, and outweighed by the potential harms. Additional testing can cause stroke, death and myocardial infarction (heart attack).
If your doctor suggests you be screened for carotid stenosis, ask why, what the best and worst outcomes could be, what the treatment options are for each and what other options are available besides screening.
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