Measuring the ankle-brachial index (ABI). The ABI is 95% sensitive and 99% specific for angiographically measured lower extremity arterial stenosis of 50% or greater. The ABI is calculated as the ratio of Doppler recorded systolic pressures in the lower and upper extremities. DP=dorsalis pedis; PT=posterior tibial. Adapted with permission of the Massachusetts Medical Society from N Engl J Med. 2001;344:1608-1621.[47]

the ankle-brachial index (ABI) is highly sensitive and specific for angiographically confirmed PAD.[22-25] The ABI is a ratio of Doppler-recorded systolic pressures in the lower and upper extremities. The ABI requires approximately 10 minutes to perform. It is a noninvasive and reliable measure of the presence and severity of PAD. To measure the ABI, systolic pressures are measured in the brachial arteries of the upper extremities and in the dorsalis pedis and posterior tibial arteries of each lower extremity with a hand-held Doppler (Figure 1). The ABI is calculated for each lower extremity by dividing the average of the posterior tibial and dorsalis pedis arterial pressures in each leg by the average of the right and left brachial artery pressures.[26] In a person without PAD, arterial pressures increase with increasing distance from the heart, resulting in an ABI >1.0.