Arterial Blood Index (ABI)

Peripheral artery disease (PAD) is a narrowing of arteries (usually in the legs and feet). When these arteries become blocked they cannot deliver an adequate blood supply to muscles and tissue. This can result in muscle cramping and pain in the legs, coldness, numbness, discoloration, and loss of hair on the feet or legs, changes in the toenails, as well as more serious complications.

A determining factor in the diagnosis of PAD is the ankle-brachial index (ABI). This is the ratio between blood pressure in the ankle and blood pressure in the upper arm. If blood pressure is lower in the ankles than in the upper arm, this may indicate that PAD is present.

The ankle-brachial index test is non-invasive and usually takes only a few minutes. Patients lie on a table while inflatable cuffs and an ultrasound device are used to listen and measure the pulse in the upper arms and then again in the ankles.

Using these numbers, the ABI can be calculated by diving the blood pressure in your ankle by the blood pressure in your upper arm. An ABI of 1.0 or greater usually indicates that your blood is flowing normally and there is no blockage. An ABI of less than 0.9 can signal a blockage and indicate the presence of PAD. In this case, the podiatrist will discuss possible next steps to help correct or improve circulation in the feet and legs.