The ankle-brachial index (ABI) is one of the most common methods used in vascular surgery to assess the severity of peripheral artery disease and the degree of limb ischemia. This metric is defined as the ratio of the ankle arterial pressure to the brachial artery pressure. ABI is obtained by measuring the pressure in the posterior or anterior tibial artery of the ankle and comparing it to the systolic pressure of the brachial artery. The tools used for measuring the ABI include blood pressure cuff and continuous waveform Doppler probe.
Limitation in the use of ABI include abnormal values in patients with severe middle calcification of arteries seen in diabetic patients or in patients at the middle stage of renal disease, accompanied by stenosis or occlusion of distal abdominal aorta or common iliac artery. In these cases, the ABI is not a reliable metric for diagnosis.

