Peripheral arterial disease (PAD) is one of the common cardiovascular diseases. According to REACH Registry, there are around 25 million PAD patients in the world, most of which are suffering from diabetes mellitus, leading to the narrowing of arteries to the legs. Moreover, the risk of suffering from cardiovascular diseases in PAD patient is many times higher than normal individuals.

One in five PAD patients may die in the short term, or experience heart attack and stroke. Ankle-brachial index (ABI) has been widely used in screening and evaluating the severity of PAD.