Is carotid ultrasound being used appropriately?

2014 02 18 12 29 39 212 Question Mark Blue 200

Over 90% of the carotid ultrasound studies performed in patients who later received carotid revascularization for asymptomatic carotid disease were ordered based on indications not considered appropriate under current guidelines, according to research published online April 18 in JAMA Internal Medicine.

The retrospective study included patients in the Veterans Health Administration (VHA) system who were 65 years or older and underwent carotid revascularization for asymptomatic carotid stenosis. Only 5.4% of the 4,063 carotid ultrasound scans were determined to be appropriate, the researchers found. What's more, long-term survival rates did not differ significantly between patients based on whether their indications were appropriate, were inappropriate, or had uncertain appropriateness.

The results highlight the need to improve the evidence base of carotid ultrasound testing, according to the team led by Dr. Salomeh Keyhani of the University of California, San Francisco.

"Clarifying and harmonizing current guidelines and the development of evidence-based decision-support tools to support appropriate patient selection for carotid imaging in practice can reduce the use of low-value imaging and improve long-term patient outcomes," Keyhani and colleagues wrote.

Conflicting guidelines

While up to 15% of ischemic strokes are caused by carotid atherosclerosis, national guidelines differ on the role of carotid screening in asymptomatic patients. The U.S. Preventive Services Task Force has recommended against carotid screening in these patients, while other national guidelines support imaging for some limited indications in patients with asymptomatic carotid disease, according to the authors.

As another complicating factor, the American Academy of Family Physicians, American Academy of Neurology, and Society of Thoracic Surgeons have all included carotid artery stenosis screening in their lists of low-value tests to be avoided as part of the Choosing Wisely campaign. The researchers also noted that while asymptomatic carotid artery disease patients receive the majority of revascularization procedures, the evidence of clinical benefit in this population isn't as robust as it is for treating symptomatic disease.

"Therefore, ensuring that patients selected for revascularization will live long enough to benefit is critical, and improving patient selection for carotid imaging will ultimately improve the selection of revascularization recipients," they wrote.

Seeking to ascertain why asymptomatic carotid disease patients were receiving carotid imaging, the team retrospectively reviewed 4,063 VHA patients who were 65 or older and had received carotid revascularization for asymptomatic carotid stenosis between 2005 and 2009. The patients were nearly all men and had an average age of 73; co-existing conditions included hypertension, diabetes, and atrial fibrillation. Carotid endarterectomy was performed on 83% of patients, while 16.8% of the patients received carotid stenting.

Overall, there were 5,226 indications for the 4,063 carotid ultrasound scans; a single indication was listed for 75.4% of the studies, while the remainder had multiple indications. Of the 57 unique indications identified in the study, two -- carotid bruit (30.2%) and follow-up for patients with previously documented carotid stenosis (20.8%) -- made up more than half of the reported indications.

Low appropriateness rate

In reviewing the indications for the carotid ultrasound studies, a multidisciplinary panel found that only 5.4% were considered to be appropriate; 11.3% were deemed inappropriate. The panel ranked the remaining 83.4% of the studies as having uncertain appropriateness due to a lack of evidence base; approximately one-third of the listed ordering indications were not addressed by current national guidelines, according to the authors.

Follow-up within two years of carotid intervention was the most common appropriate carotid imaging indication, while carotid bruit and follow-up for established carotid disease were the most prevalent uncertain indications, according to the group. The inappropriate carotid imaging indications included dizziness/vertigo, syncope (fainting), and blurred/change in vision.

"Consideration should be given to improving the evidence base around carotid testing, especially around monitoring stenosis over long periods and evaluating carotid bruits," the authors wrote.

Life expectancy

Because guidelines currently recommend providing revascularization only to patients with a five-year life expectancy, the researchers also studied the long-term survival rates for the patients in the study.

Overall, there was a 71.4% five-year survival rate. Of the patients ages 65 to 74 who received revascularization, 75.3% were still alive five years later; patients ages 75 to 84 had a five-year survival rate of 66.5%. Patients 85 and older had a 58.9% five-year survival rate. The differences between the groups were statistically significant (p < 0.001).

Five-year survival rates for patients based on carotid imaging indication were as follows:

  • Imaging based on indications with uncertain appropriateness: 72.1%
  • Imaging based on inappropriate indications: 68.8%
  • Imaging based on appropriate indications: 66.4%

The differences between the groups were not statistically significant, however (p = 0.07).

In commenting on the similarity in long-term survival rates, the researchers noted that once carotid stenosis is identified, revascularization may be provided without fully considering a patient's life expectancy.

"Although patient reassurance, clinician uncertainty, and other reasons might underlie test ordering regardless of patient eligibility, these findings could suggest that guideline development and decision support for carotid imaging ordering in an asymptomatic patient should more fully address eligibility for intervention at the time of initial test ordering," they wrote.

The results also suggest that reducing inappropriate carotid imaging may stem a "pipeline" of low-value care, according to the authors. Many patients who received revascularization had initial imaging due to inappropriate reasons.

"Reducing low-value carotid imaging can also reduce low-value carotid intervention in patients who will not live long enough to benefit," they wrote. "Given that carotid imaging is a fairly commonly ordered test, targeting carotid imaging using decision-support tools to reduce inappropriate use may be a good approach to improve the value of healthcare without compromising quality."

In good news, the researchers pointed out that the ongoing Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial (CREST-2) being sponsored by the U.S. National Institutes of Health should clarify the value of revascularization in asymptomatic patients.

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