Ankle-Brachial Index Test
This test is done by measuring blood pressure at the ankle and in the arm while a person is at rest. Measurements are usually repeated at both sites after 5 minutes of walking on a treadmill.
The ankle-brachial index (ABI) result is used to predict the severity of peripheral arterial disease (PAD). PAD refers to blockages in the arteries of the lower extremities. A slight drop in your ABI with exercise means that you probably have PAD. This drop may be important because PAD can be linked to a higher risk of heart attack or stroke.
Why It Is Done
This test is done to screen for peripheral arterial disease of the legs. This is usually done in patients complaining about leg pain with walking and who are at risk for vascular disease.
Normal
A normal resting ankle-brachial index is 1 or 1.1. This means that your blood pressure at your ankle is the same or greater than the pressure at your arm, and suggests that you do not have significant narrowing or blockage of blood flow.
Abnormal
A resting ankle-brachial index of less than 1 is abnormal. If the ABI is:
- Less than 0.95, significant narrowing of one or more blood vessels in the legs is indicated.
- Less than 0.8, pain in the foot, leg, or buttock may occur during walking.
- Less than 0.4, symptoms may occur when at rest.
- 0.25 or below, severe limb-threatening PAD is probably present.
A very abnormal ABI test result may require more testing to determine the location and severity of PAD that might be present.
