What Is an Ankle-Brachial Index Test?

Did you know your ankle, of all places, may have something important to reveal about your health?

An ankle-brachial index (ABI) test is a simple way for your doctor to check how well your blood is flowing.

She would use this test to check for peripheral artery disease, or PAD. This means you have blockages in the arteries of your arms and legs. This slows down your blood flow, and your limbs don’t get as much of the oxygen they need.

If you have PAD, you’re more likely to have a stroke or heart attack.

The test compares the blood pressure at your ankle with the blood pressure at your arm. The results can help you decide whether you need to make changes to your lifestyle or take medicine.

When Do I Need the Test?

You might need the ankle-brachial index test for a few reasons:

1. Your chances of PAD are higher than normal.

You’re more likely to get PAD as you get older. Even if you don’t have any symptoms, you may want to get the test if you’re 70 or older.

You’re also more likely to have this kind of low-flow problem if you’re 50 or older and you have any of these:

2. You have symptoms of PAD.

The main thing you may notice is pain in your legs when you walk or climb stairs. They might feel heavy, numb, or weak.

You may also have these symptoms:

  • Less hair on your legs than normal
  • One leg feels colder
  • Skin looks pale or kind of blue
  • Sores on your toes, feet, and legs that don’t seem to heal
  • Toenails grow more slowly than they once did
  • Trouble getting an erection, often in men with diabetes

3. You already know you have the condition.

If you know you have PAD, your doctor might use the test to see how your treatment has worked so far.

What Happens

The test lasts 10 to 15 minutes. First, you lie down on a table. Your doctor uses a cuff that wraps around your arm to take your blood pressure. You’ll feel a mild pressure while it inflates, but that doesn’t last long.

Continued

Your doctor will use what’s called a Doppler ultrasound device -- a plastic tool that’s a little smaller than a computer mouse. It connects to a speaker and lets your doctor hear your blood flow.

To use the device, your doctor will first put a dab of gel on your arm just below the blood pressure cuff. Then, she’ll place the ultrasound device on the gel. This helps your doctor know when to take your blood pressure reading.

She will do the same steps on your other arm, then on both ankles.

If you have leg pain and your doctor wants to make sure it’s PAD, you might take an exercise ankle-brachial index test. For this, you’ll have two ankle-brachial index readings -- one before and one after walking on a treadmill.

What Do the Results Mean?

Your doctor uses the blood pressure results to come up with a number called the ankle-brachial index. Here’s what the numbers mean:

  • 0.9 or less. You have PAD. The lower the number, the more blockage you have.
  • 1.0-1.4. You don’t have PAD.
  • Over 1.4. The test isn’t helpful to you. This result means you have stiff arteries, and you can’t get useful blood pressure numbers with the cuff. Your doctor will turn to a different test.

If you took an exercise ankle-brachial index test, the range of results may be a little different. Your doctor will look at your results, symptoms, and health history to help you decide what comes next.

You may need changes to your lifestyle or to start taking medicine. In some cases, your doctor may suggest surgery.

If you have severe PAD, your doctor may send you to a vascular specialist, a doctor who treats diseases in arteries and veins.

WebMD Medical Reference Reviewed by James Beckerman, MD, FACC on July 06, 2018

Sources

SOURCES:

Mayo Clinic, “Ankle-Brachial Index.”

National Institutes of Health, National Heart, Lung, and Blood Institute, “Explore Peripheral Artery Disease.”

Mayo Clinic, “Peripheral Artery Disease.”

Stanford Medicine, “Ankle-Brachial Index.”

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