Ankle-Brachial Index

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The ankle-brachial index test determines how well your blood is flowing by comparing the blood pressure in your legs to the blood pressure in your arms.

What Is an Ankle-Brachial Index Test?

The ankle-brachial index (ABI) test is a painless exam that is used to diagnose peripheral arterial disease (PAD). The ABI compares blood flow in the ankles and arms, detecting poor circulation that can be caused by fatty plaque buildup. During the ABI, inflatable cuffs are used on your arms and ankles to measure your blood pressure. Once the cuffs are deflated, a Doppler ultrasound is also used on your ankle to listen to your arteries. To determine the ABI, the systolic blood pressure (the top number of a blood pressure reading) of the ankle is divided by the systolic blood pressure of the arm. The simple ABI test takes less than 15 minutes to perform at a physician’s office.

When arteries in the arms and legs become obstructed by plaque, PAD occurs. The primary symptoms of PAD are:

Pain in your calves, thighs, hips or buttocks
Cramping
Weakness
Symptoms that worsen with activity and are relieved with rest

It is important to notify your physician right away if you experience any of these symptoms. Patients with PAD are at a greater risk for a heart attack or stroke.

What to Expect During Your Ankle-Brachial Index Test

Preparing for Your Procedure

No special preparation is necessary for the ABI test.

During Your Procedure

The ABI test is painless and non-invasive, although you might feel slight pressure when the cuffs are inflated. You will lie down on the exam table and blood pressure cuffs will be attached to your arms and legs. Stay still, breathe normally and relax. The ABI test usually lasts about 15 minutes or less.

After Your Procedure

Your physician will give you the ABI results and discuss the appropriate next steps. Your results will fall into one of the following categories:

ABI of 1.0 or greater: Your blood flow is in normal range.
ABI of 0.5 – 0.9: These results fall into the abnormal category. Depending on your test results, your physician may prescribe medications or order additional testing. You may also be referred to a vascular specialist.
ABI of less than 0.5: This range indicates severe PAD. Your physician will determine additional diagnostic measures and medications.