Asymptomatic adults in the general population who have no history of stroke, transient ischemic attack, or neurologic signs or symptoms should not be screened for carotid artery stenosis, according to a U.S. Preventive Services Task Force recommendation published online July 7 in Annals of Internal Medicine.
All screening strategies, even a noninvasive one that has minimal harmful effects such as ultrasonography, are insufficiently sensitive for detecting the condition. And all of them can lead to unnecessary treatment or can themselves induce serious harms including death, stroke, and myocardial infarction. Therefore, at this time, "the harms of screening for asymptomatic carotid artery stenosis outweigh the benefits," said Dr. Michael L. LeFevre of the University of Missouri, Columbia, and his associates with the USPSTF.
The recommendation is an update of the previous one issued in 2007, which also concluded that screening the general population for carotid stenosis was unwarranted. For this update, the USPSTF performed an exhaustive review and meta-analysis of the data that have accrued since that time, which addressed advances in screening tests, risk stratification tools, both screening and treatment using carotid endarterectomy (CEA) and carotid angioplasty and stenting (CAAS), and optimal medical therapies.
Dr. LeFevre, a cochair of USPSTF, and his colleagues reviewed recent randomized controlled trials, meta-analyses, and cohort studies of these topics. They found that the prevalence of carotid artery stenosis is only 0.5%-1% in the general population of adults. The most feasible screen for the condition is duplex ultrasonography; but in real-world practice, even this screen yields many false-positive results in such patients, and so exposes them to harm.
There also is no evidence that another noninvasive screen for carotid artery stenosis – auscultation of the neck to detect carotid bruits – is accurate or provides any benefit. Only four studies examined this strategy; none of them used angiography as a gold standard for diagnosis, and only two involved patients from the general population.
Moreover, even when screening of asymptomatic patients leads to detection and early intervention, "the magnitude of benefit is small to none." In particular, adding medications to current optimal medical management does not appear to convey any benefit, Dr. LeFevre and his associates said.
On the other side of the benefit-to-harm scale, carotid endarterectomy is associated with a 30-day rate of stroke or mortality of approximately 2.4% overall. However, the rates are as high as 5% in low-volume medical centers and 6% in certain states. The 30-day rate of stroke or mortality associated with CAAS is 3.1%-3.8%. Those risks are far too high to counterbalance the small benefit of screening, the USPSTF reviewers noted.
Other important harms after CEA or CAAS include myocardial infarction, surgical complications, cranial nerve injury, lung embolism, pneumonia, and local hematoma requiring further surgery.
The review and meta-analysis were hampered by a dearth of high-quality data. Specifically, much more data are needed comparing patient outcomes after CEA or CAAS with those after optimal medical therapy. The planned CREST-2 (Carotid Revascularization Endarterectomy vs Stenting Trial 2) will include a comparator group on medical management alone, and should provide important findings in this regard, Dr. LeFevre and his associates said.
They added that the USPSTF recommendation against screening the general population for carotid stenosis agrees with recommendations from the American Heart Association, American Stroke Association, American College of Cardiology, American Association of Neurological Surgeons, American College of Radiology, American Society of Neuroradiology, Society for Vascular Surgery, Society for Vascular Medicine, and the American Academy of Family Physicians.
More information on this recommendation – as well as recommendations for the related issues of hypertension, dyslipidemia, CHD, and diet – is available at the USPSTF website.
The USPSTF is an independent group that makes recommendations about the effectiveness of specific preventive care services and is funded by the Agency for Healthcare Research and Quality.