When the ankle-brachial index (ABI) emerged in 1950, it was initially proposed for use as a noninvasive diagnostic tool for lower-extremity peripheral artery disease (PAD). Since then, studies have shown that the ABI is an indicator of atherosclerosis at other vascular sites, making it a useful prognostic marker for cardiovascular events and functional impairment, even in the absence of symptoms of PAD.

via Standardizing ABI Measurements & Interpretations | Physician’s Weekly.