What is an ankle-brachial index test?

The ankle-brachial index test is a painless exam that is used to diagnose peripheral arterial disease. The ankle-brachial index test compares blood flow in the ankles and arms, detecting poor circulation that can be caused by fatty plaque buildup. During the ankle-brachial index test, 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 ankle-brachial index, 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 ankle-brachial index test takes less than 15 minutes to perform at a physician’s office. 

When arteries in the arms and legs become obstructed by plaque, peripheral artery disease occurs. The primary symptoms of peripheral artery disease 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 peripheral artery disease are at a greater risk for a heart attack or stroke.  

What to expect during an ankle-brachial index test 

Preparing for your procedure 

No special preparation is necessary for the ankle-brachial index test. 

During your procedure 

The ankle-brachial index test is painless and noninvasive, 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 ankle-brachial index test usually lasts about 15 minutes or less. 

After your procedure 

Your physician will give you the ankle-brachial index test results and discuss the appropriate next steps. Your results will fall into one of the following categories: 
  • Ankle-brachial index of 1.0 or greater: Your blood flow is in normal range.  
  • Ankle-brachial index 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.  
  • Ankle-brachial index of less than 0.5: This range indicates severe peripheral artery disease. Your physician will determine additional diagnostic measures and medications. 

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