The ankle-brachial index test is a quick, noninvasive way to check your risk of peripheral artery disease (PAD). Peripheral artery disease is a condition in which the arteries in your legs or arms are narrowed or blocked. People with peripheral artery disease are at a high risk of heart attack, stroke, poor circulation and leg pain.The ankle-brachial index test compares your blood pressure measured at your ankle with your blood pressure measured at your arm. A low ankle-brachial index number can indicate narrowing or blockage of the arteries in your legs, leading to circulatory problems, heart disease or stroke. The ankle-brachial index test is sometimes recommended as part of a series of three tests, including the carotid ultrasound and abdominal ultrasound, to check for blocked or narrowed arteries.