Ankle-Brachial Index (ABI) Test: Detecting Peripheral Artery

Peripheral artery disease (PAD) is a long-term circulatory disorder characterised by narrowed arteries that decrease blood flow to the limbs, mostly the legs. Peripheral artery disease in India is estimated to affect 5–25% of the population, per the 2023 Indian Consensus Statement for the Management of Lower Extremity PAD.

The ankle brachial pressure index test is an essential diagnostic tool for the early identification of PAD.

What Is the Ankle-Brachial Index (ABI) Test?

The ankle brachial index (ABI) test, or the ankle brachial pressure index (ABPI) test, is a non-invasive and rapid test used to determine blood flow in the lower limbs. It compares systolic blood pressure readings in brachial arteries (upper arms) and dorsalis pedis or posterior tibial arteries (ankles) using a Doppler ultrasound device.

Ankle brachial pressure index (ABPI) is calculated by dividing the blood pressure found in the ankle by the blood pressure found in the arm. The index helps identify arterial blockages that can indicate the presence or severity of peripheral artery disease (PAD).

How Does the Ankle Brachial Pressure Index Work?

The ankle brachial pressure index test is usually completed within 10-15 minutes. It involves the following steps:

• Positioning: The patient lies down on the examination table. Socks and shoes are taken off. Accurate baseline readings are recorded while resting for 5-10 minutes.
• Blood Pressure Cuffs: Inflatable cuffs are placed on both arms and ankles.
• Doppler Ultrasound: A handheld Doppler Probe with ultrasound gel is used to measure and detect the audible blood flow in the arteries.
• Inflation and Observation: The cuff is inflated until blood flow stops, then deflated steadily as the probe detects returning blood flow, which is marked as systolic pressure.
• Calculation: The maximum ankle systolic pressure is divided by the highest arm systolic pressure to calculate each leg’s ankle brachial pressure index.

How to Prepare for the Ankle Brachial Pressure Index Test?

Preparing for an ankle brachial pressure index test is simple. One can follow these steps to ensure comfort and accurate results:

1. Choose comfortable clothes for easy access to arms and ankles.
2. Do not consume caffeine, tobacco products, or alcohol for at least one hour before the test.
3. Avoid physical activity at least an hour before the test.
4. Use the restroom before the test.
5. Mention any previous leg procedures or circulatory treatments.

What Are the Risks Associated with the ABI Test?

The following precautionary steps can be taken for the ankle brachial pressure index (ABI) test:

1. Temporary discomfort can be caused by cuff inflation, but it is expected to go away quickly. If the pain is too much, inform the provider.
2. Cuffs should not be put on ulcers or open wounds. The doctor may prescribe an alternate testing procedure.
3. Inform the provider about any recent bypass surgery, as cuff pressure can be unsafe post-surgery.
4. The ABI test is generally avoided if a clot is suspected in the leg.
5. Severe leg pain may require imaging instead of pressure-based testing.

What Do the Results of the ABI Test Mean?

An ankle brachial index below 0.90 is generally considered low and indicates the presence of peripheral artery disease (PAD). This happens due to narrowing of the arteries, reducing blood flow to the legs, causing pain, numbness, and fatigue.

The following is what the ankle brachial pressure index indicates:

1. Above 1.4: Hardened arteries; ABI may not be reliable in this case, and there may be a need to use an alternative test, such as the toe-brachial index.
2. 1.0 to 1.4: Normal; no severe blockage.
3. 0.91 to 0.99: Borderline PAD; possible requirement of an exercise ABI test.
4. 0.70 to 0.90: Mild PAD; requires lifestyle changes or medication as advised.
5. 0.40 0.69: Moderate PAD; may require imaging or expert care.
6. Less than 0.40: Substantial PAD; would probably require surgery.

Follow up with the healthcare provider after receiving results to understand the situation better.

Who Should Get an ABI Test?

The ABI pressure test is recommended in the following cases:

1. People over the age of 65, or 50+, especially those who smoke, have  diabetes, high blood pressure, or cholesterol.
2. People with leg pain during physical activity or who have poor wound healing.
3. Have a family history of PAD.

The ABI ankle brachial index test is a quick and painless way to detect peripheral artery disease symptoms early, monitor progression, and reduce serious risks like stroke or limb loss.

Consult a doctor, download the Dr Lal PathLabs app, and book a test today.

FAQs

1. What is an ABI test done for?

It checks for peripheral artery disease (PAD) by comparing blood pressure in the arms and ankles to detect low blood flow.

2. What is a normal ABI level?

A normal ABI ankle-brachial pressure index ranges from 1.0 to 1.4, which indicates normal blood pressure to the legs without arterial narrowing.

3. What is ABI analysis?

ABI analysis measures blood flow by comparing ankle and arm pressures to detect blockages and diagnose peripheral artery disease (PAD).