PAD is greatly underdiagnosed. Many patients do not report symptoms, or may not even have symptoms. People should be checked for peripheral artery disease if they have leg pain during walking, or ulcers on their legs.
The doctor should check for high blood pressure, heart abnormalities, blockage(s) in the artery in the neck, and abdominal aneurysms. The doctor should also examine the skin of the legs and feet for color changes, ulcers, infection, or injuries, and check the pulse of the arteries in the leg.
Intermittent claudication caused by peripheral artery disease is typically diagnosed using a calculation called the ankle-brachial index. This method also helps to diagnose PAD in patients without symptoms of intermittent claudication.
The procedure is done as follows:
- The doctor or technician measures the systolic blood pressure of both arms while the patient is lying down. (The systolic pressure is the "top" number in a blood pressure measurement. It is the force that blood exerts on the artery walls as the heart contracts to pump out the blood. For example, in a blood pressure reading of 120/80, 120 is the systolic number.)
- The doctor or technician then puts blood pressure cuffs on four different locations on each leg and passes a Doppler probe over arteries in the foot. The signal emitted from the strongest artery is recorded as the cuffs are inflated and deflated. This is the ankle's systolic pressure.
The doctor divides the systolic pressure in the ankle by the systolic pressure in the arm. The result is called the ankle-brachial index (ABI), also called ankle-arm pressure index (API).
What the results mean:
- ABI over 0.90. This result often rules out PAD, but if the patient has specific risk factors for artery disease, the doctor may still suspect PAD. In such cases, the patient takes a treadmill test and another ABI measurement. If the API index drops, the doctor makes a diagnosis of peripheral artery disease.
- ABI below 0.90. This is usually sufficient information to diagnose PAD. The lower the index the greater the risk for heart attack, stroke, or other serious circulatory or heart events. (In patients with diabetes, the doctor may perform additional tests, which may include ultrasound, pressure measurement in the first toe, or others that might confirm or dismiss a diagnosis of PAD.)
- ABI less than 0.50. These measurements are highly associated with impaired leg function.
- ABI less than 0.40. These measurements indicate very severe blockage in the leg arteries and a risk for gangrene.
Review Date: 04/05/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.