LEAD (Lower extremity arterial disease) is a chronic, progressive disease that can lead to lower extremity wounds, infection, pain, loss of limb and impaired quality of life. A significant percentage of individuals are afflicted with LEAD, but many more go undiagnosed because they are either asymptomatic or unreliable methods are being utilized to make the diagnosis and provide appropriate treatment. The Ankle Brachial Index (ABI) is a valid, reliable, non-invasive test that provides an objective indicator of arterial perfusion to a lower extremity, thus supporting the diagnosis of vascular disease. This document provides relevant information about the ABI including definition, limitations, indications, contraindications, and guidelines, and a research-based protocol to use in performing the test and interpreting the results. Publish Date: 11/7/11; 19 page document.