The ankle-brachial index is a simple, noninvasive test to check for peripheral artery disease (PAD). It’s a quick outpatient test that measures the blood pressure at your ankle compared with the blood pressure at your arm.
The results are determined by dividing the blood pressure in an artery of the ankle by the blood pressure in an artery of the arm. A low ankle-brachial ratio or index number can be an indication of PAD.
Why Do You Need an Ankle-Brachial Index?
Your doctor may order an ankle-brachial index if you have leg pain while walking or have any of the following risk factors for PAD:
- Being older than age 70, or being younger than 50 with diabetes and one additional risk factor
- High blood pressure or cholesterol
The test can also be done to check the severity of PAD if you’ve already been diagnosed. It may be something your doctor orders annually.
Getting Ready for an Ankle-Brachial Index
Minimal preparation is needed for this test. You may want to wear loose clothing so the technician can easily place the blood pressure cuffs on your arm and ankle. When you schedule your appointment, ask if there are any additional instructions you may need to follow before your test.
What to Expect During an Ankle-Brachial Index
You’ll need to rest for at least 15 to 30 minutes before the procedure. During the test, you will lie on the table while a technician measures your blood pressure in both arms and both ankles. Testing generally lasts 10–20 minutes, depending on how many times your blood pressure is taken.
The technician will calculate the results by dividing the blood pressure in your ankle by the blood pressure in your arm. A low ratio indicates potential PAD. These results will be shared with your doctor, who will share them with you.
Depending on your doctor’s schedule, you may or may not receive the results that day.