Ankle-brachial index (ABI)
Ratio of ankle to brachial pressure. Below 0.90 confirms peripheral artery disease, above 1.40 indicates calcification.
Updated · Methodology
Systolic pressure is measured with a Doppler probe, supine, after 5 to 10 minutes of rest.
About this calculator
Each leg's index is the higher of the posterior tibial and dorsalis pedis pressures on that leg, divided by the higher of the two brachial pressures. The patient's overall figure is taken from the leg with the lower value, because the diagnosis follows the worse limb. Thresholds from the AHA 2012 statement: above 1.40 non-compressible arteries, 1.00-1.40 normal, 0.91-0.99 borderline, 0.41-0.90 mild to moderate disease, 0.40 and below severe. A value above 1.40 is often read as good flow, which is a mistake: it means the arterial wall is calcified and does not yield to the cuff. This occurs in diabetes and chronic kidney disease, and calls for a toe-brachial index or duplex ultrasound instead. A second limitation: in some patients with intermittent claudication the resting ABI is normal, and the abnormality appears only after treadmill exercise testing. The measurement is made with a Doppler probe, supine, after 5 to 10 minutes of rest. Auscultating Korotkoff sounds at the ankle will not do: arterial sounds are often inaudible there and the result comes out falsely low.
Source
Formula version: aboyans-aha-2012-v1
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