What is the gold standard for the evaluation of peripheral artery disease (PAD)?

• A. Toe-brachial index
• B. CTA or MRA
• C. Ankle-brachial index (ABI) calculated by dividing the higher leg systolic pressure by the higher brachial artery systolic pressure
• D. Duplex ultrasound

Answer: (C)

Ankle-brachial index is the standard first-line, noninvasive test used to evaluate peripheral artery disease. It compares blood pressure in the legs with blood pressure in the arms to gauge how well blood is reaching the lower extremities. To perform it, you take the systolic pressures in the legs and use the higher leg pressure as the numerator and the higher of the two brachial pressures as the denominator. A value below 0.90 indicates PAD and generally correlates with disease presence and severity. This test is favored because it is quick, inexpensive, widely available, and has good diagnostic performance for detecting PAD, including in people who might not yet have symptoms. In cases where arteries are heavily calcified (common in diabetes or CKD), the ABI can be unreliable, so the toe-brachial index or further imaging is used. Other imaging tests, like CTA/MRA or duplex ultrasound, provide detailed anatomy and are helpful for planning interventions or when the ABI is inconclusive, but they are not the primary diagnostic standard. Invasive catheter angiography is more definitive for detailing the exact vessel lesions and is typically reserved for planning revascularization rather than initial diagnosis.