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Ankle-Brachial Index Test - Why Is It Done?

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The ankle-brachial index is a quick test that is done to check the presence of any peripheral vascular disease.

Medically reviewed by

Dr. Sathis Kumar. S

Published At May 4, 2022
Reviewed AtFebruary 14, 2024

Introduction

The ankle-brachial index (ABI) test is a high-speed test. It is non-invasive. It is one of the ways to check for the existence of any peripheral artery disease or PAD. Peripheral artery disease occurs when the coronary arteries or any other arteries of the body turn highly narrow. The narrowing of arteries leads to a reduction in the flow of blood to the limbs and extremities. Peripheral artery disease has the potential to develop severe pain in the limbs during activities such as walking and running. In addition to this, it may also increase the risk of an episode of heart attack as well as stroke.

The ankle-brachial index compares the blood pressure of the ankle and the blood pressure of the arm. A low ankle-brachial index may be indicative of blockages present in arteries in the lower limbs. The ankle-brachial index testing can be done before or after walking. It can also be done using a treadmill. To assess the severity of the blockage present, an exercise ankle-brachial index test can be conducted.

Why Might Someone Need an Ankle-Brachial Index Test?

Numerous researches have identified the occurrence of peripheral artery diseases in about 10 % of individuals above the age of 55 years. The ankle-brachial index test is suggested to investigate the appearance of peripheral artery disorder. The healthcare provider may recommend taking an ankle-brachial index test if the patient has persistent pain in the extremities, especially the legs, during certain activities such as walking. Several other reasons suggest an ankle-brachial index test, such as those mentioned below.

How to Read the Result of an Ankle-Brachial Index Test?

The healthcare provider will use the measurements and readings of blood pressure from the patient’s arms and legs, mainly from the ankle, to calculate the ankle-brachial index. Based on the reading, the ankle-brachial index is calculated as mentioned below.

  • No Arterial Blockage - An ankle-brachial index number in the range of 1.0 to 1.4 suggests the absence of peripheral artery disease. Nevertheless, if the patient has signs and symptoms of peripheral artery disease, the healthcare provider might offer an exercise ankle-brachial index test.

  • Borderline Arterial Blockage - An ankle-brachial index number in the range of 0.91 to 0.99 indicates borderline peripheral artery disease. The healthcare provider might additionally recommend an exercise ankle-brachial index test.

  • PAD - An ankle-brachial index number less than 0.90 is considered highly abnormal and strongly suggests a positive diagnosis of peripheral artery disease. The healthcare provider may recommend supplemental tests, such as exercise ankle-brachial index test, ultrasound, and angiography, to investigate the arteries of the lower limbs.

In case the patient has a long history of severe diabetes or the presence of significant blockage of arteries, they may be asked for additional tests to read the blood pressure of the big toe. This is referred to as the toe-brachial index, and it aids in obtaining a more accurate test result.

What Are the Risks of an Ankle-Brachial Index Test?

Ankle-brachial index test is a noninvasive test. It hardly poses any risk to the patient. Some individuals may feel a slight amount of discomfort as and when the cuffs to measure one's blood pressure start to be inflated in the arm as well as the ankle. This kind of discomfort is short-term. Being temporary, the discomfort stops as soon as the air is released. In case there is severe pain in the legs, the healthcare provider and team may suggest an alternative imaging test for the arteries of the legs.

How to Get Ready for an Ankle-Brachial Index Test?

There are no specific preparations required before an ankle-brachial index test. Being noninvasive, the test is quite comfortable and parallel checking one's blood pressure during a routine consultation. Therefore, it is better to wear loose-fitting attire as well as comfortable clothing. This will allow the professional team performing the ankle-brachial index test to wrap the blood pressure cuff on both the arm and the ankle smoothly.

What to Expect During an Ankle-Brachial Index Test?

During the procedure on an ankle-brachial index test, the patient is likely to be asked to rest for 10 to 30 minutes before the test. Then, in a typical setup, the patient is asked to lie flat on a table on their back while a professional begins to measure the patient’s blood pressure in both arms as well as both ankles. This measurement takes place with the help of an inflatable cuff and an ultrasound that is hand-held on the skin. This device captures sound waves and produces the pulse to be clearly heard in the arteries of the ankle once the cuff has been deflated. After the procedure is completed, there is no need to follow any precautions.

What Happens After an Ankle-Brachial Index Test?

After an ankle-brachial index test, individuals can normally resume their regular activities immediately. Following up with a doctor regarding the results is necessary. In certain instances, additional tests such as an MRI (magnetic resonance imaging) or arteriogram may be done to obtain further information on a blocked vessel.

For those diagnosed with PAD, potential treatments include cessation of smoking, management of conditions like high blood pressure, high cholesterol, and diabetes if necessary, maintaining physical activity, adopting a healthy diet, taking medications to improve blood flow to the legs or prevent blood clots, undergoing procedures like angioplasty to restore blood flow, or in severe cases, undergoing leg surgery.

What Are the Advantages of the Ankle-Brachial Index Test?

ABI is a reliable tool for assessing vascular health, helping to prevent complications associated with PAD. Advantages of the ABI test include its

  • Non-invasive nature.

  • Simplicity.

  • Cost-effectiveness.

  • No long-term effects.

  • Done as an outpatient procedure.

Conclusion

The ankle-brachial index test is a measurement and comparison between the blood pressure of the arms and the legs. Ankle-brachial tests can predict mortality as well as the onset of cardiovascular events. Therefore, the ankle-brachial index is a vital diagnostic tool. It is important to note that alternate clinical manifestations of peripheral vascular disease, such as pain with walking, numbness of the extremities, weakness, palpitations, and yellowish discoloration of the legs, should also be taken into account while diagnosing peripheral artery disease. Post the test, a change to a healthier and more active lifestyle may be suggested.

Frequently Asked Questions

1.

How Is an ABI Test Done? Who Performs It, and Can It Be Painful?

The ankle-brachial index test is done by a clinical technician, where the patient’s blood pressure is measured from both arms, and the values are assessed. The procedure, when performed, can be quite uncomfortable but not painful.

2.

What Does a Positive ABI Test Indicate, and When Is It Normal?

The normal average value of the ABI test is around 1.10 to 1.40. Still, a positive ABI test is indicated when the ratio goes above 1.4, showing a positive indication of stiffness of the blood vessels in the limbs.

3.

How Is Blocked Artery in the Leg Treated?

The block in the artery reduces the blood flow, and to fix this it is managed by surgically removing the affected area, replacing it with a graft, and putting the patients on blood thinners.

4.

What Is the Importance of the ABI Test, and When Is It Indicated?

An ankle brachial index test is performed to analyze the difference in blood pressure between the upper and lower limbs. It is indicated to examine patients who complain of leg pain while walking.

5.

What Is the Cause for Blockage in the Leg?

The blockage of the blood vessels occurs due to hardening and narrowing of the blood vessels that is caused by underlying health conditions like:
- Increased blood cholesterol.
- Diabetes.
- Calcification of the blood vessels, etc.

6.

How Is an ABI Test Interpreted?

The ankle-brachial test is interpreted as:
- 1.0 - 1.4 - considered normal and indicates higher ankle pressure than limbs.
- Above 1.4 - noncompressible calcified vessel.
- Less than 0.9 - is a diagnostic value of possible peripheral arterial disease.
- Less than 0.5 - severe peripheral artery disease.

7.

In What Ways Can We Increase Blood Circulation in Legs?

Blood circulation in the legs can be increased naturally by:
- Walking
- Compression elastic stockings.
- Messages.
- Sauna baths or hydrotherapy.
- Stretching exercises.
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Dr. Sathis Kumar. S
Dr. Sathis Kumar. S

General Medicine

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