The ABI

Were you recently screened for peripheral arterial disease?
Legs for Life™ conducted nationwide, free, screening programs in the fall, and the American Vascular Association conducted free screenings last May. Perhaps you participated and received a free screening but are curious to learn more about the test they gave and what the results mean. The following information should help (it can also be found on our web site at www.vdf.org):

The ankle-brachial index (ABI) exam is a simple and reliable means to help diagnose peripheral arterial disease (PAD). Blood pressure measurements are taken at the arms and ankles using a pencil shaped ultrasound device called a Doppler. A Doppler instrument produces sound waves (not x-rays) and is considered noninvasive because it does not require the use of needles or catheters. Not only is the ABI one of the most reliable tests for PAD, it is also the least expensive.

What happens during the exam?
While lying on your back, standard blood pressure cuffs are placed around your ankles and arms. These cuffs are inflated briefly above your normal systolic blood pressure. Once the cuffs are deflated, blood pressure measurements are taken using the Doppler instrument.

The arm and ankle systolic blood pressure measurements are recorded. Then the ankle systolic pressures are divided by the highest arm pressure to establish an ABI measurement for each leg.

What do the measurements mean?
The doctor or technician will determine a number that usually is between .4 and 1.2 and these numbers are typically interpreted as:

.91 – 1.2 *		Normal
.90 or lower		Presence of PAD
.40 or lower		Severe PAD

*A measurement great than 1.2 is probably due to noncompressible arteries as a result of long-standing diabetes, old age or calcification in the arteries. In these cases the ABI cannot be relied on to detect PAD.

What other exams will work?
For patients with such rigid ankle blood vessels, toe pressure measurements can be given. This examination is called a toe brachial index (TBI) and is a calculation based on the systolic blood pressures of the arm and the systolic blood pressures of the toes. The examination is similar to the ABI except that it is performed with a photoplethysmograph (PPG) infrared light sensor and a very small blood pressure cuff placed around the toe. A TBI of .8 or greater is considered normal. Alternatively, a leg arterial ultrasound test can detect PAD if the ABI is not considered reliable.

What should happen after the exam?
If you receive a measurement that indicates PAD is present, you should call your physician and make an appointment to discuss the resultsÑbe sure to take the results with you. You can also call a local vascular specialist. For more information on the ABI, visit our web site and click our button for Peripheral Arterial Disease. You'll find the information listed under "Diagnosis."