What Is an Ankle-Brachial Index Test?
An ankle-brachial index (ABI) test is a simple way for your doctor to check how well your blood is flowing.
They use this test to check for peripheral artery disease (PAD). When you have this condition, it means you have blockages in the arteries of your arms and legs. This slows your blood flow, so your limbs don’t get all the oxygen they need.
The ABI test compares the blood pressure at your ankle with the blood pressure at your arm. If you have a low score on this test, you probably have poor blood flow in your legs.
Why the Ankle-Brachial Index Test Is Done
You might need the ankle-brachial index test for a few reasons:
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 blood flow problem if you’re 50 or older and you have any of these:
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 heal the way they should
- Toenails that grow more slowly than they once did
- Trouble getting an erection, often in men who have diabetes
You know that you have PAD.
If you know you have it, your doctor might use the test to see how your treatment has worked.
Ankle-Brachial Test Procedure
The test lasts 10 to 15 minutes. First, you lie down on a table. Your doctor wraps a cuff around your arm to take your blood pressure. You’ll feel mild pressure while it inflates, but that doesn’t last long.
Your doctor will use a Doppler ultrasound device, a plastic tool that’s a little smaller than a computer mouse. It connects to a speaker so they can 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, they’ll put the ultrasound device on the gel. This helps them know when to take your blood pressure reading.
They’ll do the same steps on your other arm and 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.
Ankle-Brachial Index Test Risks
This test doesn’t usually have risks. Your doctor will probably use a different test if you have a blood clot in your leg or if you have serious leg pain.
Ankle-Brachial Test Results
Your doctor uses the blood pressure results to come up with a number called an 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 in your arteries.
- 0.91-0.99. This result is acceptable but might mean that you have borderline PAD.
- 1.0-1.4. You don’t have PAD.
- Over 1.4. Numbers this high mean you have stiff arteries, and you can’t get useful blood pressure numbers with the cuff. Because of this, the test isn’t helpful for you. 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 to change your lifestyle or start taking medicine. In some cases, your doctor may say you need surgery.
If you have severe PAD, your doctor may send you to a vascular specialist, a doctor who treats diseases in arteries and veins.