The ankle-brachial index test is a quick, noninvasive way to check your risk of peripheral artery disease (PAD). Peripheral artery disease is a condition in which the arteries in your legs or arms are narrowed or blocked. People with peripheral artery disease are at an increased risk of heart attack, stroke, poor circulation and leg pain.
The ankle-brachial index test compares your blood pressure measured at your ankle with your blood pressure measured at your arm. A low ankle-brachial index number can indicate narrowing or blockage of the arteries in your legs, increasing your risk of circulatory problems, and possibly causing heart disease or stroke.
The ankle-brachial index test is sometimes recommended as part of a series of three tests, including the carotid ultrasound and abdominal ultrasound, to check for blocked or diseased arteries.
Why it's done
The ankle-brachial index test is done to check for peripheral artery disease (PAD), a condition in which the arteries in your legs or arms are narrowed.
Ask your doctor if you should have this test if you are age 50 or older and have any of these risk factors for PAD:
Being a current or former smoker
High blood pressure
If you've already been diagnosed with PAD, your doctor may recommend having an ankle-brachial index test to see if your treatment is working or if your condition has worsened.
If you have symptoms of PAD, your doctor may suggest you have an exercise ankle-brachial index test to determine if your symptoms, such as leg pain with walking, are due to PAD or other conditions, such as spinal stenosis. In an exercise ankle-brachial index test, you walk on a treadmill for a short time before your ankle-brachial index is measured.
When the ankle-brachial index test is complete, your doctor calculates your ankle-brachial index by dividing the systolic blood pressure (top number) at the arteries near your ankle by the systolic blood pressure in the arms. Compared to the arm, lower blood pressure in the leg is an indication of PAD.
Based on the number your doctor calculates, your ankle-brachial index may show you have:
No blockage (1.0 to 1.4).An ankle-brachial index number in this range suggests that you probably don't have peripheral artery disease. But if you have certain risk factors, such as diabetes, smoking or a family history of PAD, tell your doctor so that he or she can continue to monitor your risk.
Blockage (0.9 or less).An ankle-brachial index number less than 1.0 indicates narrowing of the arteries in your leg. Depending on how low the number is, blockage may range from mild to severe, indicating mild to severe PAD.
Rigid arteries (more than 1.4).If your ankle-brachial index number is higher than 1.4, this may mean that your arteries are rigid and don't compress when the blood pressure cuff is inflated. You may need an ultrasound test to check for peripheral artery disease instead of an ankle-brachial index test, or a toe-brachial index test, in which the blood pressures in your arm and big toe are compared.