USPSTF: Insufficient evidence for ankle-branchial index screening

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 US 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 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. 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 six percent 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.