Medical knowledge, Patient Education
Ankle-Brachial Index Test
Why am I having this test?
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Cholesterol deposits in your blood vessels (atherosclerosis). This is the most common cause of this condition.
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Inflammation in the blood vessels.
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Blood clots in the vessels.
Cholesterol deposits cause arteries to narrow. Decreased delivery of oxygen to your tissues causes muscle pain, cramping, and fatigue that occurs during exercise and is relieved by rest. This is called intermittent claudication.
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In your heart. This raises the risk of heart attacks.
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In your brain. This raises the risk of strokes.
What is being tested?
The ankle-brachial index test measures the blood flow in your arms and legs. The blood flow will show if blood vessels in your legs have been narrowed by cholesterol deposits.
How do I prepare for this test?
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Wear loose, comfortable clothing with shoes that are easy to remove.
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Do not use any products that contain nicotine or tobacco for at least 30 minutes before the test. These products include cigarettes, chewing tobacco, and vaping devices, such as e-cigarettes.
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Avoid caffeine, alcohol, and heavy activity an hour before the test.
What happens during the test?
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You will lie down in a resting position with your legs and arms at heart level.
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Your health care provider will use a blood pressure machine and a small ultrasound device (Doppler) to measure the systolic pressures on your upper arms and ankles. Systolic pressure is the pressure inside your arteries when your heart pumps.
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Systolic pressures will be taken several times, and at several points, on both the ankle and the arm. Your health care provider may also measure your toe.
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Your health care provider will divide the highest systolic pressure of the ankle by the highest systolic pressure of the arm. The result is the ankle-brachial pressure ratio, or ABI.
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Sometimes this test will be repeated after you have exercised on a treadmill for 5 minutes. You may have leg pain during the exercise portion of the test if you suffer from PVD. If the index number drops after exercise, this may show that PVD is present.
How are the results reported?
Your test results will be reported as a value that shows the ratio of your ankle pressure to your arm pressure (ABI ratio). Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). These ranges may vary among labs and hospitals.
For this test, an abnormal reading is typically considered, which is an ABI ratio of 0.9 or less.
What do the results mean?
An ABI ratio that is below the reference range is considered abnormal and may indicate PVD in the legs.
Talk with your health care provider about what your results mean.
Questions to ask your health care provider
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When will my results be ready?
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How will I get my results?
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What are my treatment options?
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What other tests do I need?
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What are my next steps?
Summary
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The ankle-brachial index (ABI) test is used to diagnose peripheral vascular disease (PVD). PVD is also known as peripheral arterial disease (PAD).
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The ABI test measures the blood flow in your arms and legs.
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The highest systolic pressure of the ankle is divided by the highest systolic pressure of the arm. The result is the ABI ratio.
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An ABI ratio of 0.9 or less is considered abnormal and may indicate PVD in the legs.
This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.
