Preventive MedicineProcedures

SCREENING FOR CAROTID ARTERY DISEASE

Oh, no! Not again! You know that United States Preventive Services Task Force (USPSTF) I’ve written about so many times? Well, they just came up with another doozy! All these people do is find reasons to shoot holes in every screening test they can think of. Their mission, it seems, is to shake the confidence of the public in the value of preventive medicine. This at a time when, after forty years of pleading, physicians have finally convinced patients of the value of check-ups and preventive screenings. Patients have accepted the commitment to be pro-active; to do things that promote good health and detect problems before they have disastrous results.  

Their justification for recommending against a screening is their over-concern about the harms that might possibly result from these procedures. They often say the risks outweigh the benefits and lead to unnecessary testing or treatment, or surgeries fraught with serious complications.

This time they recommended against screening for asymptomatic carotid artery disease. The carotid arteries are the main blood supply to the brain. A blockage (stenosis) of one carotid causes stroke-like symptoms on the opposite side of the body. The right carotid carries blood to the right side of the brain. A stroke or TIA (Transient Ischemic Attack—temporary cutoff of blood to the brain) in the right brain causes paralysis on the left side of the body. The goal of screening is to find a blockage early, and treat it before it causes a devastating stroke.

Three types of screening are done: ultrasound, CT angiogram, MRI angiogram. Ultrasound is the most frequently done and the easiest of the three. It’s the procedure mobile diagnostic vans perform for a fee on patients who sign up for screenings. 

“The prevalence of asymptomatic carotid artery stenosis is low in the general population but increases with age.” The consequences of an untreated blockage are serious enough, however,  that the USPSTF decided to take a second look at the value of these screenings. They conclude, once again, that they could find “ no new substantial evidence that could change its recommendation and had “moderate certainty that the harms of screening…outweigh the benefits….no studies have directly looked at whether screening….decreases the rates of stroke or death.” 

My conclusion differs from theirs! If your meadow is not getting enough water because the beavers have partially dammed the stream, you get rid of the beavers (cholesterol) and remove the dam (arteriosclerotic plaque). You don’t have any studies to show the grass in the meadow will die, but you intellectually know not getting enough water will be a problem (a stroke). So you have to go upstream and look to see if the beavers have been at work. You don’t know there’s a problem upstream until you look for it (screening ultrasound).

The USPSTF, though, says if you find the start of a dam, it will be too expensive to remove it, and you might damage the shoreline or make the beavers extinct if you do something about it. Or some of the dam might break loose and block a small tributary. They say, “If it ain’t broke, don’t fix it,” but don’t try to find a problem because it may be risky to fix it and may not be necessary. I say “bunk!” Every now and then, you need to look upstream to see if the beavers have been at work. Keeping the stream open is important to the meadow below. You don’t want to wait until the stream is completely blocked. You may lose your crop or livestock.

No sooner do I praise the USPSTF for their tobacco cessation position than they come out against carotid screening because it “has no benefit and may be harmful.” Sure, “harm” is possible, but it’s possible during a coronary bypass operation, too, and they don’t think twice about recommending that. So practically and realistically speaking, I opine on the side of screening to keep the number of admissions to nursing homes on the low end. I would much rather take the risk of carotid surgery than spend years unable to move or speak in a nursing home. That is the most cost-effective approach ever. 

References: JAMA Patient Page: Screening for Carotid Artery Stenosis. JAMA 2021 Feb 2;325(5):500.

USPSTF. Screening for Asymptomatic Carotid Artery Stenosis. JAMA 2021 Feb 2;325(5):476-481. 

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