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An Ankle-Brachial Index (ABI) is a simple, non-invasive test used to assess blood flow in the limbs and is particularly useful in diagnosing peripheral artery disease (PAD). In individuals with PAD, there is a blockage or narrowing of the arteries that supply blood to the legs, which typically results in decreased blood flow.

When measuring ABI, the systolic blood pressure in the ankle is compared to the systolic blood pressure in the arm. In a healthy individual, the pressure in the ankle should equal or exceed the pressure in the arm due to the proximity of the heart and the fact that the legs are receiving proper blood flow.

In persons with PAD, the condition results in lower blood pressure readings at the ankle compared to the arm because the narrowed arteries limit the blood flow. Therefore, a lower ankle pressure indicates impaired circulation as a consequence of arterial disease.

Thus, correctly interpreting a lower ankle pressure than arm pressure signifies the presence of PAD and is reflected in the ABI calculation, which indicates that blood flow to the ankle is compromised. Understanding this relationship helps healthcare professionals effectively gauge the severity of PAD and determine appropriate management strategies.