Ankle-brachial index test

Exam Overview

This test is done by measuring blood pressure at the ankle and in the arm while a person is at rest. Measurements are then 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). A decrease in the ABI result with exercise is a sensitive indicator that significant PAD is probably present.

Why It Is Done

This test is done to screen for peripheral arterial disease of the legs.

Results

The resting ABI result can help diagnose peripheral arterial disease (PAD). If the index number drops after exercise, this may mean that significant PAD is present.

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 there is no 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 exercise (intermittent claudication).
• Less than 0.4, symptoms may occur when at rest.
• 0.25 or below, severe limb-threatening PAD is probably present.

What To Think About

You may experience leg pain during the treadmill portion of the test if you have peripheral arterial disease (PAD).

Undiagnosed arterial disease in the arms can cause inaccurate test results.

Blood pressure readings may not be accurate when the blood vessel being measured is hardened by calcium (calcified). Arteries may calcify more than usual if you have diabetes or kidney problems (renal insufficiency).¹

A very abnormal ABI test result may require more testing to determine the location and severity of PAD that might be present.

Complete the medical test information form (PDF) (What is a PDF document?) to help you prepare for this test.

Author:	Shannon Erstad, MBA/MPH Ralph Poore	Last Updated November 3, 2005
Medical Review:	Martin Gabica, MD - Family Medicine Kathleen Romito, MD - Family Medicine David A. Szalay, MD - Vascular Surgery
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