The ABI provides a measure of peripheral artery disease (PAD) and is simple and inexpensive to perform. Calculation is by measuring the systolic blood pressure (by Doppler probe) in the brachial, posterior tibial, and dorsalis pedis arteries. The higher ankle measurement is divided by the higher brachial measurement.
ABI 1.0–1.3 is the normal value. Values >1.3 suggest a non-compressible calcified vessel.
ABI below 0.9 is associated with a >50% stenosis in one or more major vessels and has a 95% sensitivity for detecting angiogram-positive PAD.
ABI 0.4–0.9 suggests arterial obstruction often associated with claudication.
ABI <0.4 represents advanced ischemia.
ABIs typically correlate with the clinical measures of lower extremity function such as walking distances, balance, and overall physical activity. Lower ABIs correlate with a higher risk of coronary artery disease (CAD), stroke, progressive renal insuffi cency, and all-cause mortality.
Reference: Oxford American Handbook of Cardiology.