Ankle Brachial Index | ABI Calculator

Highest pressure in both arms

Highest pressure in right foot

Highest pressure in left foot

ABI Value	Vessel structure interpretation	Recommendation
1.0 - 1.4	Normal	None
0.9 - 1.0	Acceptable	None
0.8 - 0.9	Some Arterial Disease	treat risk factors
0.5 - 0.8	Moderate Arterial Disease	Refer to vascular specialist
< 0.5	Severe Arterial Disease	Refer to vascular specialist

The ABI has been demonstrated to predict mortality and unfavorable cardiovascular events without conventional CV risk variables. All patients over 70, smokers over 50, diabetics over 50, and smokers over 50 are advised to have their ABIs measured, according to major cardiovascular organizations.

The qualitative and quantitative data comprise the two portions of an ankle-brachial index (ABI) report. The patient’s blood pressure readings from both arms and ankles are included in the quantitative section, along with the ABI ratios.

In this article, you’ll learn more about its objective, the results, and how to calculate ABI (Ankle-Brachial Index). Even though it’s crucial to remember that this calculator does not replace a thorough medical examination, you can use it if you’re unsure whether to speak with your doctor about your blood pressure and the likelihood that you will eventually acquire a cardiovascular illness.

How is the ABI calculator used?

Use the methods below to determine your ankle-brachial index using an ABI calculator:

Start by entering the highest systolic pressure measured in both arms into the ABI calculator.
Each leg’s ankle-brachial index is calculated separately:
To get your right ABI, enter the blood pressure reading that was the highest in your right leg.
To get your left ABI, enter the blood pressure reading that was the highest in your left leg.

A doctor must perform the blood pressure measurement in order to calculate your ABI because it is a bit more difficult than a routine blood pressure test. It is absolutely safe and non-invasive, and your doctor will walk you through it. However, suppose you smoke, and you can’t quit right away. In that case, you must cease at least two hours before the test to reduce the chance that smoking-related peripheral artery vasoconstriction will occur and alter the results.

Interpreting the Ankle-Brachial Index

To interpret the ankle-brachial index results, Stanford Medicine offers the following guide.

ABI	Interpretation	Recommended action
Above1.4	The result indicates calcification or vessel hardening.	Consult a vascular specialist!
1.0 – 1.4	Normal	No action is needed.
0.9 – 1.0	Acceptable	No action is needed.
0.8 – 0.9	A mild arterial disease might be present.	Consult your doctor about the result and treat risk factors accordingly to their recommendations.
0.5 – 0.8	Moderate arterial disease.	Consult a vascular specialist!
Below 0.5	Severe arterial disease.	Consult a vascular specialist!

How to Calculate ABI?

Although you can be sure that your doctor can calculate ABI, learning how to do it yourself could help you feel more confident. The ABI calculator’s formula is quite straightforward. This is how it works:

Left ABI = highest left ankle systolic pressure / highest brachial systolic pressure

Right ABI = highest right ankle systolic pressure / highest brachial systolic pressure

Systolic blood pressure is the force exerted by the heart’s contraction on the blood vessel walls. That is the first (and higher) of the two readings for blood pressure. For instance, the systolic pressure is 120 if your doctor informs you your blood pressure is 120 over 80.
The term “brachial” refers to the upper arm’s brachial artery.

When is the ankle-brachial index calculated?

Peripheral artery disease, a condition that causes the arteries to constrict and obstructs adequate blood flow, is diagnosed with ABI. Since this issue mostly affects the legs, doctors typically advise getting an ABI test if you have leg pain when moving around, especially if PAD risk factors are present. These include a history of smoking, diabetes, high blood pressure, or high cholesterol.

FAQs

What is a normal ABI Score?

The typical ABI ranges from 1.10 to 1.40. This is because in people without PAD, the lower extremity arteries’ systolic pressures rise at the ankle compared to the brachial arteries as the distance between the arteries and the heart increases. This is because the arteries’ impedance increases as the arterial taper increases.

How accurate is the ABI test?

The ABI test has an accuracy of about 95% for identifying PAD. A normal ABI score does not, however, completely eliminate the chance of PAD in some people. ABI values that are normal or almost normal in certain patients may show little signs of PAD.

How to Measure the Brachial Pressure?

The patient should be lying on his or her back. The arm should be at the same level as the heart when the blood pressure cuff is applied. Put the ultrasound gel on the patient’s brachial pulse in the antecubital fossa. Place the handheld Doppler’s transducer on the gel, and position it so that the signal is as strong as possible. Set the cuff’s pressure to roughly 20 mmHg higher than the patient’s anticipated systolic blood pressure. The Doppler signal ought to vanish. After that, deflate the cuff gradually (1 mmHg/sec). The cuff’s pressure is equal to the systolic brachial pressure when the Doppler signal reappears. The systolic brachial pressure should be noted.

How to Measure the Ankle Pressures?

1. Placing the cuff close to the malleoli is recommended. Apply ultrasonic gel to the skin that covers the foot’s posterior tibial (PT) and dorsalis pedis (DP) arteries. The DP’s Doppler signal is frequently located a little to the lateral of the foot’s dorsum’s midline. Find the signal from the DP using an ordinary handheld Doppler probe and the ultrasonic gel. Move the Doppler slowly until you can hear the loudest signal. Inflate the cuff until you don’t need to hear the signal in order to measure the systolic pressure at the DP artery. Once the Doppler signal reappears, gradually deflate the balloon using the same method as with the arms. Take note of the measurement.
2. The PT artery’s systolic pressure should then be determined. A posterior to the medial malleolus PT signal is found. To test the PT systolic pressure once more, find the signal using the Doppler with ultrasound gel and proceed as before. On the other leg, repeat the two measurements.

Conclusion

Taking ABI tests or understanding how to calculate ABI and utilizing the ABI calculator is absolutely important if you want to check your ankle-brachial index and see if you are at risk for peripheral artery disease.