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USPSTF: Insufficient evidence for ABI screening in asymptomatic adults

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ABI remains useful

The USPSTF’s conclusion that current evidence is insufficient to recommend screening for PAD and cardiovascular risk with the ABI in asymptomatic adults should not be misconstrued as a determination that PAD is not common, clinically important, or associated with significant adverse outcomes.

Dr. Mary McDermott of Northwestern University, Chicago M. Alexander Otto/MDedge News

Dr. Mary McDermott

The recommendation does not apply to people with ischemic symptoms during walking activity, who should be tested for PAD with the ABI. The ABI is important for diagnosing nonspecific leg symptoms, common in older people at risk for PAD who frequently have comorbidities such as spinal stenosis, arthritis, and neuropathy that contribute to leg symptoms. The USPSTF recommendation does not apply to these people.

Because most people with PAD do not have classic symptoms of intermittent claudication, the ABI is an important clinical tool for diagnosing PAD and identifying people at increased risk of cardiovascular events and functional decline.

Mary McDermott, MD , is a professor of internal medicine, geriatrics, and preventive medicine at Northwestern University, Chicago, and a JAMA senior editor. Michael Criqui, MD , is a professor of family medicine and public health at the University of California, San Diego. They made their comments in an editorial. Dr. McDermott disclosed research funding from Novartis and Regeneron ( JAMA. 2018 Jul 10;320[2]:143-5 ).



There’s not enough evidence to recommend – or not recommend – routine ankle-brachial index screening for peripheral artery disease in asymptomatic adults without known cardiovascular or chronic kidney disease, according to the U.S. Preventive Services Task Force.

“A substantial number of asymptomatic persons with low ABI may never develop clinical signs or symptoms of CVD or PAD but would still be subjected to the harms of testing,” including false positives, exposure to gadolinium or contrast dye with subsequent imaging, and others, the Task Force wrote in JAMA.

In short, it found “inadequate evidence to assess whether screening for and treatment of PAD in asymptomatic patients leads to clinically important benefits in either preventing the progression of PAD or preventing CVD events. ... The current evidence is insufficient to assess the balance of benefits and harms of screening for PAD and CVD risk with the ABI in asymptomatic adults.”

The group made no recommendation, and issued an I statement, for insufficient evidence, July 10. The new work replaces the Task Force’s last visitation in 2013, which was also an “I statement.”

ABI is systolic blood pressure at the ankle divided by the systolic blood pressure in the arm while the patient is lying down. A ratio below 1 is considered abnormal.

ABI is low in perhaps about 6% of adults over 40 years old but “the natural history of screen-detected PAD, including the development of morbidity and mortality directly related to atherosclerosis in the lower limbs, is not well known. ... Large, population-based, randomized trials of screening [versus] no screening are needed to determine whether screening for PAD with the ABI improves clinical outcomes,” the task force said.

Among the many studies it reviewed were two large trials of asymptomatic women with low ABI treated with aspirin 100 mg/d for several years. Neither study showed any significant difference in CVD events, mortality, or development of intermittent claudication.

Even in high-risk people – diabetes, high blood pressure, high cholesterol, current tobacco use – there was “no compelling evidence” to support routine screening, so long as they have no symptoms.

The new review is broader than the group’s 2013 effort, and includes a broader population and range of interventions. Even so, “the recommendation remains an I statement,” it said.

The USPSTF is supported by the U.S. Agency for Healthcare Research and Quality.

SOURCE: JAMA. 2018 Jul 10;320(2):177-83

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