Ankle-Brachial Index (ABI) Test
An ankle-brachial index test can help a physician diagnose peripheral artery disease. The ankle-brachial index (ABI) test is a relatively simple diagnostic procedure that compares the blood pressure in the arms with the blood pressure in the legs. The ABI is calculated by dividing the blood pressure measured in an artery in an ankle by the blood pressure measured in an artery in an arm. An ABI of less than 0.9 may be a sign of peripheral artery disease, which occurs when the arteries that supply blood to the legs become narrowed by cholesterol plaque.
A physician may order an ankle-brachial index test for a patient who is experiencing symptoms of peripheral artery disease, which include:
- Leg pain that worsens with activity and improves with rest
- Muscle cramping in the hips, thighs or calves after walking or climbing stairs
- Leg muscle weakness or numbness
- A cold sensation in one leg or foot
- Sores on the legs, feet or toes that do not heal
- A change in the color of the skin on the legs
- Hair loss or slow hair growth on the legs
- Slow toenail growth
- A weak pulse in the legs or feet
An ABI test may also be appropriate for a patient who has certain risk factors for peripheral artery disease, such as high cholesterol, high blood pressure, diabetes or a history of tobacco use.
An ankle-brachial index test is similar to a routine blood pressure test. While the patient lies comfortably on an examination table, a technician will measure the patient’s blood pressure in both arms and both ankles using an inflatable cuff and a hand-held ultrasound device placed over an artery. The ultrasound device will allow the technician to hear the blood flowing through the vessel.
To obtain each measurement for the ankle-brachial index test, the technician will inflate the cuff until blood stops flowing through the vessel, then slowly release the air from the cuff. When the technician hears the blood begin to flow again, he or she will record the systolic pressure, which will be used to calculate the ABI.
What to Expect
There is minimal risk associated with an ABI test. Some patients experience mild discomfort when the blood pressure cuffs are inflated. The discomfort is temporary and will resolve when the air is released from the cuffs.
The ankle-brachial index test is highly effective for screening patients who are at risk for peripheral artery disease. This simple, non-invasive test is also effective for diagnosing patients who have symptoms of peripheral artery disease.
Tampa General Hospital’s Heart & Vascular Institute offers the latest screening and diagnostic options for peripheral artery disease, including the ABI test.