American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What does an Ankle-Brachial Index (ABI) of less than 0.9 indicate?

1. Normal blood flow

2. Claudication

3. Rest pain

4. Critical limb ischemia

The correct answer is: Claudication

An Ankle-Brachial Index (ABI) of less than 0.9 is indicative of some level of arterial obstruction in the lower extremities, often associated with peripheral arterial disease (PAD). Although values below 0.9 may suggest claudication, which is characterized by pain or discomfort in the legs during physical activity due to inadequate blood flow, it is also important to note that this range can encompass varying degrees of arterial insufficiency beyond just claudication. Typically, an ABI between 0.4 and 0.9 is categorized as mild to moderate peripheral artery disease, where patients may experience claudication—muscle pain that occurs during exercise but is relieved with rest. Values below 0.4 are suggestive of more severe ischemia, potentially leading to rest pain and critical limb ischemia. In sum, while an ABI of less than 0.9 is consistent with the presence of claudication (an inadequate blood supply to the muscles during activity), it may also reflect early stages of more significant arterial disease. Understanding the broader implications of ABI readings aids in determining the extent of vascular compromise and guiding further management.