The United States Preventive Services Task Force (USPSTF) decided that current evidence is insufficient to recommend screening for peripheral artery disease (PAD) and cardiovascular risk with the ankle-brachial index (ABI) in asymptomatic adults.
In this report, published in JAMA, the USPSTF updated its 2013 recommendations, this time expanding the review to include patients with diabetes and interventions that include supervised exercise and physical therapy intended to improve outcomes in the legs.
PAD affects an estimated 8.5 million adults in the United States. Most people with PAD do not have classic symptoms of intermittent claudication, or pain in the legs that worsens with activity and gets better with rest.
The USPSTF recommendation does not apply to people with ischemic symptoms during walking activity, who should be tested for PAD with the ABI.
The ABI is calculated as systolic blood pressure as measured at the ankle divided by systolic blood pressure as measured at the arm (brachial artery) while lying down. An index of less than 0.9 is considered abnormal and is commonly used to define PAD.
The USPSTF decision applies specifically to using the ABI as a screening tool in patients without signs or symptoms of disease.
The task force reviewed the evidence on whether screening for PAD with the ABI in generally asymptomatic adults reduces morbidity or mortality from PAD or cardiovascular disease (CVD). The USPSTF found few data on the accuracy of the ABI for identifying asymptomatic persons who can benefit from treatment of PAD or CVD.
There are few studies addressing the benefits of treating patients detected by screening with PAD, the report said. Two good-quality studies showed no benefit of using the ABI to manage daily aspirin therapy in unselected populations, and 2 studies showed no benefit from exercise therapy.
Although there are minimal harms associated with the ABI test, subsequent harms are possible. Those include false-positive test results, false-negative test results, anxiety, exposure to gadolinium or contrast dye from confirmatory MRA or CTA, stress tests, angiographs, or prescription medicine that could have adverse effects or, conversely, reclassify a patient to a lower risk category, which could have an unintended consequence if they later give up beneficial treatment.
Low ABI has been used as a proxy for PAD, but its accuracy as a screening tool in asymptomatic primary care populations has not been well studied. The time and resources needed to screen with the ABI in primary care may take away from other health activities that may have more benefit, the report noted.
Therefore, the balance of benefits and harms of screening for PAD with the ABI in asymptomatic adults cannot be determined, and the current evidence is Insufficient, the task force said.