What is ankle-brachial index (ABI) measurement? 3 steps for accurate results

According to medical studies, peripheral artery disease (PAD) affects over 230 million people worldwide, yet many cases go undiagnosed until dangerous complications such as stroke, myocardial infarction, or heart failure appear. Alarmingly, arterial narrowing or blockage often progresses silently for many years without causing clear symptoms.

Ankle-brachial index (ABI) measurement is a simple, non-invasive yet highly valuable method for early detection of peripheral artery disease, assessing the risk of vascular occlusion, atherosclerosis, and related cardiovascular diseases. By comparing blood pressure at the ankle with blood pressure at the arm, this index helps doctors identify abnormalities in blood flow to the legs.

In this article, Tiptory will guide you on how to measure ABI, explain the meaning of each result, and help you understand when to perform this test to protect your cardiovascular health early on.

Ankle-Brachial Index (ABI) Measurement

Step 1: Position the patient correctly

Before performing an ankle-brachial index (ABI) measurement, the patient needs to lie on their back on a bed or a firm surface.

• Keep the body relaxed for about 5–10 minutes.
• Do not cross legs or bend knees.
• Limit physical activity before the measurement for more accurate blood pressure results.

Step 2: Wrap blood pressure cuffs

Prepare appropriate blood pressure cuffs and secure them in the correct positions.

• Wrap cuffs above the ankles of both legs.
• Wrap cuffs around the arm, just above the elbow.
• Ensure the cuffs fit snugly, not too loose or too tight.

Step 3: Measure brachial artery blood pressure

Proceed to measure blood pressure at the brachial artery as a reference value.

• Locate the brachial artery.
• Record the highest systolic blood pressure reading obtained.
• This is an important data point for calculating the ABI.

Step 4: Measure dorsalis pedis artery blood pressure

Next, measure blood pressure at the dorsalis pedis artery.

• Place the probe or measuring device correctly over the artery.
• Record the systolic blood pressure for each leg.
• Perform carefully to avoid inaccurate results.

Step 5: Measure posterior tibial artery blood pressure

Also measure blood pressure at the posterior tibial artery.

• Locate the artery behind the medial malleolus.
• Record the systolic blood pressure for both the left and right legs.
• Compare with the results measured at the dorsalis pedis artery.

Step 6: Calculate the ankle-brachial index (ABI)

After completing the measurements, proceed to calculate the ABI.

1. Select the highest systolic blood pressure value for each ankle.
2. Select the highest systolic blood pressure value at the arm.
3. Divide the ankle blood pressure by the arm blood pressure.

Formula:

ABI = Highest ankle systolic blood pressure ÷ Highest arm systolic blood pressure

This result helps assess the status of peripheral artery disease, lower limb arterial stenosis, atherosclerosis, and the risk of future cardiovascular diseases.

Part 1: How to accurately measure arm blood pressure using a Doppler machine

Step 1: Position the patient correctly before ABI measurement

Place the patient supine on a flat surface

The standard position for performing an ankle-brachial index (ABI) measurement is supine (lying on the back) on a flat and firm surface.

• The head, torso, and legs should be aligned.
• Avoid elevating the head or propping up the legs too high.
• Keep the body relaxed throughout the measurement process.

The correct posture helps ensure that the ankle-brachial blood pressure measurement results accurately reflect blood flow in the arterial system.

Ensure arms and legs are at heart level

The position of the limbs can directly affect blood pressure measurement results.

• Both arms and both legs should be positioned at heart level.
• Do not let the arms hang down or raise them too high.
• Limit movement while performing the measurement.

This helps reduce errors when assessing peripheral artery disease and issues related to lower limb blood circulation.

Allow the patient to rest for at least 10 minutes

Before the measurement, allow the patient to rest completely.

• Lie still for about 10 minutes.
• Avoid talking or excessive movement.
• Do not consume stimulants like coffee or tobacco immediately before the test.

Resting helps stabilize blood pressure, especially in individuals who are stressed or anxious during the examination.

Completely expose both arms

Direct contact with the measurement area helps the device function effectively and provides accurate results.

• Roll up sleeves high or wear loose clothing.
• Do not allow clothing to constrict the arm.
• Ensure the blood pressure cuff placement area is unobstructed.

This is a simple but very important preparatory step for a smooth ABI measurement, arterial occlusion assessment, and vascular health check.

Step 2: Locate the brachial artery

Find the brachial artery position before measuring blood pressure

The brachial artery is an important location for measuring blood pressure and calculating the ankle-brachial index (ABI). Accurately locating the artery will lead to more precise results when assessing peripheral artery disease.

• Use your index and middle fingers to palpate for the pulse.
• Gently move your fingertips along the anterior aspect of the elbow.
• Feel for the regular pulse of the artery beneath the skin.

Do not use the thumb to palpate the pulse

Many people are accustomed to using their thumb when checking a pulse, but this can cause confusion.

• The thumb has its own pulse, which can easily lead to perception errors.
• It is better to use the index and middle fingers to feel the pulse more clearly.
• Avoid pressing too hard, as this can make the pulse harder to detect.

Locate the antecubital fossa

The brachial artery is usually located just above the antecubital fossa, also known as the cubital fossa.

• Find the midpoint of the inner elbow when the arm is extended.
• Gently palpate above the elbow crease to find the point with the clearest pulse.
• Mark or remember this position before placing the blood pressure device.

Precisely locating the brachial artery is a crucial step in enhancing the accuracy of ABI measurement, blood flow assessment, and evaluation of arterial narrowing or occlusion risk.

Step 3: Wrap the blood pressure cuff correctly

Place the cuff on the left arm

After locating the brachial artery, proceed to wrap the blood pressure cuff around the left arm in preparation for measurement.

• Wrap the cuff around the upper arm.
• The lower edge of the cuff should be approximately 4–5 cm above the brachial artery pulse site.
• Ensure the cuff lies flat, without twisting or creasing.

Proper cuff placement helps improve the accuracy of arm blood pressure measurement and ankle-brachial index (ABI) calculation.

Adjust tightness appropriately

The tightness of the cuff directly affects the measurement results.

• The cuff should fit snugly around the arm but not be excessively tight.
• After wrapping, you should be able to slide two fingers between the cuff and the skin.
• Avoid wrapping too loosely, as the cuff may slip during measurement.

A correctly adjusted cuff helps minimize errors when assessing arterial blood flow and peripheral vascular health.

Select the appropriate cuff size

Incorrect cuff size can lead to blood pressure results that are either artificially high or low.

• The cuff width should be approximately two-thirds of the patient's arm length.
• Individuals with large arms require a larger cuff than standard.
• Individuals with small arms should choose a suitable cuff size to ensure accuracy.

Choosing the correct cuff size is a crucial step in the ABI measurement process, helping to accurately assess the risk of arterial narrowing, atherosclerosis, and peripheral artery disease.

Step 4: Measure systolic blood pressure in the arm

Place the stethoscope correctly

To accurately determine arm blood pressure when performing an ankle-brachial index (ABI) measurement, the stethoscope should be placed over the previously identified brachial artery.

• Place the diaphragm of the stethoscope directly over the brachial artery.
• Ensure good contact between the stethoscope and the skin.
• Avoid letting the stethoscope touch the cuff or clothing, as this can cause noise interference.

Correct stethoscope placement helps clearly hear vascular sounds and accurately determine blood pressure readings.

Inflate the blood pressure cuff

After placing the stethoscope, inflate the cuff to temporarily restrict blood flow through the artery.

• Close the valve of the pump bulb before inflating.
• Inflate the cuff to about 20 mmHg higher than the anticipated systolic blood pressure.
• Continue to inflate until no more arterial sounds are heard.

This step is necessary to identify the point at which blood flow returns when deflating.

Determine systolic blood pressure

Slowly deflate the cuff and listen for sounds from the artery.

• Open the valve to release air slowly and steadily.
• Monitor the blood pressure gauge while listening.
• The reading at the moment the first beat is heard is recorded as the systolic blood pressure.

Systolic blood pressure reflects the highest pressure in the arteries when the heart contracts and pushes blood throughout the body.

Understand the meaning of systolic and diastolic blood pressure

When measuring blood pressure, you will obtain two important readings.

• Systolic blood pressure: This is the maximum pressure in the arteries when the left ventricle contracts to pump blood out.
• Diastolic blood pressure: This is the minimum pressure in the arteries when the heart relaxes and the heart chambers refill with blood.

In the process of calculating the ABI, systolic blood pressure is the value used for comparison between the arm and ankle to assess peripheral artery disease, lower limb arterial stenosis, and the risk of atherosclerosis.

Step 5: Deflate and record blood pressure

Deflate the cuff slowly

After inflating the cuff to the necessary level, begin to reduce the pressure in the cuff to determine blood pressure readings.

• Open the deflate valve slowly and steadily.
• Maintain a pressure reduction rate of approximately 2–3 mmHg per second.
• Continuously monitor the blood pressure gauge throughout the deflation process.

Deflating too quickly can cause important sounds to be missed, leading to inaccurate measurement results.

Listen for the appearance of arterial sounds

As the pressure in the cuff gradually decreases, blood flow will begin to return through the artery.

• Note the moment the first beat appears in the stethoscope.
• Record the reading displayed on the blood pressure gauge at that moment.
• This is the systolic blood pressure.

Systolic blood pressure reflects the maximum pressure in the arteries when the heart contracts and pumps blood throughout the body.

Determine diastolic blood pressure

Continue to deflate slowly and observe the changes in arterial sounds.

• Observe until the beats disappear completely.
• Record the reading on the gauge at the moment the sound is no longer heard.
• This is the diastolic blood pressure.

Diastolic blood pressure represents the pressure in the arteries when the heart is at rest between beats.

Record systolic blood pressure to calculate ABI

During the ankle-brachial index (ABI) measurement, the most important value is the systolic blood pressure.

• Accurately record the measured systolic blood pressure reading.
• Use this value for comparison with systolic blood pressure at the ankle.
• This data is necessary for calculating the ABI, assessing peripheral artery disease, lower limb arterial occlusion, and the risk of atherosclerosis.

Correctly recording systolic blood pressure helps ensure that the assessment of blood circulation and vascular health has a higher degree of reliability.

Part 2: Guide to accurate ankle blood pressure measurement

Step 1: Maintain posture before ankle measurement

Keep the patient supine

After completing arm blood pressure measurement, the patient needs to continue maintaining a supine position to prepare for ankle blood pressure measurement.

• Ask the patient to lie still on a flat surface.
• Avoid sitting up, standing up, or changing position abruptly.
• Limit arm and leg movements during the measurement.

Maintaining the same posture helps ensure accuracy when performing an ankle-brachial index (ABI) measurement.

Ensure arms and legs are at heart level

The goal of this step is to maintain stable blood pressure between measurement sites.

• Both arms and both legs should be kept at the same height as the heart.
• Do not prop legs up too high or let them hang lower than the bed surface.
• Avoid placing hands on the chest or resting the head on the arm.

This helps minimize errors when comparing blood pressure between the arm and ankle to assess peripheral arterial circulation.

Remove the cuff from the arm

After fully recording arm blood pressure readings, proceed to remove the cuff to switch to measuring at the leg.

• Gently remove the cuff from the patient's arm.
• Recheck the recorded data.
• Prepare the cuff and measuring device for the ankle position.

This is an important transition step before measuring blood pressure at the ankle artery to complete the ABI calculation process, aiding in early detection of peripheral artery disease, lower limb arterial stenosis, and signs of atherosclerosis.

Step 2: Wrap the cuff around the ankle

Place the cuff on the left ankle

After completing arm blood pressure measurement, the next step is to measure blood pressure at the ankle to calculate the ankle-brachial index (ABI).

• Wrap the cuff around the left ankle.
• Position the lower edge of the cuff approximately 4–5 cm above the ankle bone.
• Ensure the cuff is evenly wrapped around the leg and not twisted.

Accurate cuff placement will help obtain more reliable ankle artery blood pressure measurements.

Check cuff tightness

The cuff needs to be secured firmly but not cause excessive compression.

• After wrapping, try to insert two fingers between the cuff and the skin.
• If two fingers can be inserted easily, the tightness is usually appropriate.
• If two fingers cannot be inserted, loosen the cuff slightly.

Wrapping the cuff too tightly can lead to inaccurate ankle blood pressure readings and affect the ABI value.

Select the appropriate cuff size

Cuff size is a crucial factor determining the accuracy of the measurement.

• Choose a cuff with a width slightly larger than the calf circumference.
• Avoid using a cuff that is too small, as it can lead to falsely high blood pressure results.
• Do not use a cuff that is too large, as it can result in falsely low readings.

Using the correct cuff size helps improve accuracy when assessing peripheral artery disease, lower limb arterial stenosis, and the status of atherosclerosis.

Recheck before measuring

Before starting the ankle blood pressure measurement, review all cuff placement locations.

• Ensure the patient remains supine and relaxed.
• Check that the cuff has not shifted during preparation.
• Confirm the measuring device is ready for operation.

Proper preparation will help ensure that the ABI measurement results accurately reflect blood flow to the lower limbs and aid in early detection of vascular diseases.

Step 3: Locate the dorsalis pedis artery

Locating the dorsalis pedis artery

The dorsalis pedis (DP) artery is one of the important sites used to measure ankle blood pressure when performing an Ankle-Brachial Index (ABI) measurement.

• The dorsalis pedis artery is located on the top of the foot.
• This position is usually near the junction between the foot and the ankle.
• The examiner needs to identify the correct position before proceeding with blood pressure measurement.

Finding the correct artery helps ensure more accurate results for assessing lower limb blood circulation.

Apply ultrasound gel to the area to be examined

Before using the Doppler probe, the skin surface needs to be properly prepared.

• Apply a sufficient amount of ultrasound gel to the top of the foot.
• Spread the gel evenly over the area where the dorsalis pedis artery is suspected.
• The gel helps increase the transmission of sound signals between the probe and the blood vessel.

This step helps the Doppler device detect blood flow more effectively.

Use a Doppler probe to locate the pulse

The Doppler probe is used to identify the location with the clearest pulse signal.

• Gently place the probe on the gel-applied area.
• Move the probe slowly in various directions.
• Adjust the contact angle until the best signal is received.

This technique is commonly used in ABI measurement to accurately detect arterial blood pressure in the leg.

Identify the point with the strongest signal

Continue moving the probe until the location with the clearest blood vessel sound is found.

• Choose the point that emits the loudest and most stable signal.
• The sound usually resembles a rhythmic beat or the sound of blood flowing.
• Mark or maintain the probe's position to prepare for blood pressure measurement.

The point with the strongest signal usually reflects the clearest dorsalis pedis artery location, which helps increase accuracy when assessing peripheral arterial disease, lower limb arterial stenosis, and other circulatory disorders.

Step 4: Measure dorsalis pedis artery blood pressure

Inflate the cuff to temporarily stop blood flow

After precisely locating the dorsalis pedis artery using the Doppler probe, proceed with ankle blood pressure measurement.

• Hold the Doppler probe at the strongest signal location.
• Inflate the cuff to approximately 20 mmHg above the usual systolic blood pressure.
• Continue inflating until the blood flow sound from the Doppler completely disappears.

When the sound signal is no longer heard, it indicates that blood flow through the artery has been temporarily blocked by the cuff pressure.

Slowly deflate the cuff and monitor the Doppler signal

After reaching the required pressure, begin to release pressure from the cuff.

• Open the deflation valve slowly and steadily.
• Observe the blood pressure monitor throughout the deflation process.
• Simultaneously listen for the sound signal from the Doppler probe.

Deflating too quickly can cause the moment the signal reappears to be missed, leading to inaccurate results.

Record ankle systolic blood pressure

As the pressure in the cuff decreases, blood flow will begin to return through the artery.

• Note the moment the blood flow sound or characteristic "whoosh" reappears on the Doppler.
• Record the reading on the blood pressure monitor at that moment.
• This is the systolic blood pressure of the dorsalis pedis artery.

This value reflects the maximum blood pressure in the ankle artery when the heart contracts.

Save the results to calculate the ABI

The systolic blood pressure measured in the dorsalis pedis artery is important data for calculating the Ankle-Brachial Index (ABI).

• Record the results immediately after measurement.
• Ensure no confusion between measurement locations on the left and right legs.
• Compare with brachial systolic blood pressure in the next calculation step.

Ankle blood pressure results help assess the level of lower limb blood circulation, aiding in early detection of peripheral arterial disease, leg arterial stenosis, arterial occlusion, and complications related to atherosclerosis.

Step 5: Locate the posterior tibial artery

Locating the posterior tibial artery

To increase the accuracy of the Ankle-Brachial Index (ABI) measurement, blood pressure needs to be measured at both the dorsalis pedis artery and the posterior tibial (PT) artery.

• The posterior tibial artery is located on the medial side of the ankle and lower leg.
• The pulse is usually found in the area behind the medial malleolus.
• This is one of the main arteries supplying blood to the foot and lower limb.

Measuring blood pressure at the posterior tibial artery provides a more comprehensive assessment of peripheral arterial circulation.

Apply ultrasound gel to the area to be examined

Before using the Doppler probe, the skin surface needs to be prepared to optimize signal reception.

• Apply a layer of ultrasound gel to the suspected area of the posterior tibial artery.
• Spread the gel evenly to enhance sound wave transmission.
• Ensure the probe directly contacts the gel-applied skin area.

Ultrasound gel helps make the Doppler signal clearer and more stable during pulse detection.

Use a Doppler probe to locate the pulse

Proceed to locate the posterior tibial artery using the Doppler device.

• Gently place the probe on the gel-applied area.
• Move the probe slowly in various directions.
• Adjust the probe angle to obtain the strongest signal.

This process helps precisely identify the location with the best blood flow before measuring blood pressure.

Identify the point with the clearest pulse

Continue scanning until a strong and stable blood vessel signal is heard.

• Choose the position that produces the clearest sound.
• The signal typically sounds like a rhythmic beat or continuous blood flow.
• Hold the probe at this position to prepare for posterior tibial artery blood pressure measurement.

Recording blood pressure at the posterior tibial artery along with the dorsalis pedis artery will help achieve more accurate ABI results, aiding in early detection of peripheral arterial disease, lower limb arterial stenosis, vascular occlusion, and signs of atherosclerosis.

Step 6: Measure posterior tibial artery blood pressure and the other leg

Measure posterior tibial artery blood pressure

After identifying the posterior tibial artery with the strongest signal, proceed to measure blood pressure similarly to the dorsalis pedis artery.

• Hold the Doppler probe at the location with the clearest pulse sound.
• Inflate the cuff to approximately 20 mmHg above the anticipated systolic blood pressure.
• Continue inflating until the blood flow signal completely disappears.
• Slowly deflate the cuff and observe the blood pressure monitor.
• Record the reading at the moment the blood flow sound reappears.

This is the systolic blood pressure of the posterior tibial artery and is important data for calculating the Ankle-Brachial Index (ABI).

Carefully record the results

After completing the measurement, save the results immediately to avoid confusion.

• Clearly record the systolic blood pressure of the posterior tibial artery in the left leg.
• Clearly distinguish between results from the dorsalis pedis artery and the posterior tibial artery.
• Double-check the data before moving to the other leg.

Thorough record-keeping makes the ABI calculation process more accurate and convenient.

Move the cuff to the right leg

After completing the measurements on the left leg, proceed to do the same with the right leg.

• Remove the cuff from the left leg.
• Wrap the cuff in the correct position on the right ankle.
• Ensure the patient maintains a supine and relaxed position.

A stable position helps minimize errors when comparing blood pressure between the two legs.

Measure dorsalis pedis and posterior tibial artery blood pressure in the right leg

Repeat the entire measurement procedure for the two main arteries in the right leg.

1. Locate the dorsalis pedis artery using a Doppler probe and measure systolic blood pressure.
2. Locate the posterior tibial artery and measure systolic blood pressure.
3. Record all measured results.

Upon completing this step, you will have all the systolic blood pressure readings from the brachial artery, dorsalis pedis artery, and posterior tibial artery of both legs to calculate the ABI, assess peripheral arterial disease, lower limb arterial stenosis, vascular occlusion, and the risk of atherosclerosis.

Part 3: ABI calculation formula and how to interpret results

Step 1: Select ankle blood pressure for ABI calculation

Consolidate ankle measurement results

After completing blood pressure measurements on both legs, gather all recorded readings.

• Left dorsalis pedis (DP) artery systolic blood pressure.
• Left posterior tibial (PT) artery systolic blood pressure.
• Right dorsalis pedis (DP) artery systolic blood pressure.
• Right posterior tibial (PT) artery systolic blood pressure.

These are the necessary data to accurately calculate the Ankle-Brachial Index (ABI).

Determine the highest reading for each leg

Each leg will have two systolic blood pressure values measured from two different arteries.

• Compare the results of the dorsalis pedis artery and the posterior tibial artery in the left leg.
• Select the higher systolic blood pressure value as the representative result for the left leg.
• Do the same for the right leg.

Using the highest value helps better reflect the actual blood pressure in the lower limbs.

Record representative ankle blood pressure

After comparison, each leg will retain only one value for calculation.

• Left leg: use the highest systolic blood pressure between the DP and PT arteries.
• Right leg: use the highest systolic blood pressure between the DP and PT arteries.

This is a standard method commonly applied in the process of assessing peripheral arterial disease.

Prepare for ABI calculation

Once the highest systolic blood pressure for each leg has been determined, you can proceed to the calculation step.

• Use the highest ankle blood pressure value for each side.
• Compare it with the brachial systolic blood pressure measured previously.
• Calculate the ABI separately for the left and right legs.

Choosing the correct ankle blood pressure helps increase accuracy in detecting lower limb arterial stenosis, peripheral vascular occlusion, atherosclerosis, and associated cardiovascular risks.

Step 2: Calculate the Ankle-Brachial Index (ABI)

Apply the ABI calculation formula

Once you have determined the highest ankle systolic blood pressure and brachial systolic blood pressure, you can proceed to calculate the Ankle-Brachial Index (ABI).

• Divide the highest ankle systolic blood pressure by the brachial artery systolic blood pressure.
• Calculate separately for the left and right legs.
• Each leg will have a separate ABI result.

Formula:

ABI = Ankle systolic blood pressure ÷ Brachial systolic blood pressure

This is a common method for assessing peripheral arterial disease, lower limb arterial stenosis, and the status of blood circulation in the legs.

Calculate ABI for the left leg

Use the highest systolic blood pressure value measured in the left ankle.

• Select the highest result between the dorsalis pedis (DP) and posterior tibial (PT) arteries of the left leg.
• Divide this value by the brachial artery systolic blood pressure.
• Record the result for final assessment.

Example:

• Left ankle systolic blood pressure: 120 mmHg
• Brachial systolic blood pressure: 100 mmHg

Calculation:

• Left leg ABI = 120 ÷ 100 = 1.20

Calculate ABI for the right leg

Perform similarly for the right leg.

• Select the highest systolic blood pressure between the DP and PT arteries of the right leg.
• Divide by the brachial artery systolic blood pressure.
• Record the result to compare with the other leg.

Calculating each leg separately helps detect cases of arterial occlusion or stenosis that occur only in one lower limb.

Review results before evaluation

After completing the calculation, it is advisable to review all data.

• Confirm that the highest systolic blood pressure for each ankle was used.
• Ensure the correct brachial artery systolic blood pressure was used as the reference value.
• Double-check the division to avoid errors.

The ABI is a simple yet highly valuable tool for screening for atherosclerosis, peripheral arterial disease, reduced blood flow to the legs, and the risk of future cardiovascular events.

Step 3: Interpret and evaluate ABI results

Record the ABI for each leg

After completing the calculation, record the Ankle-Brachial Index (ABI) results for both the left and right legs.

• Save the results in the tracking record or examination sheet.
• Compare the values between the two legs to detect any abnormal differences.
• Use the results to assess the status of lower limb blood flow and the risk of peripheral arterial disease.

The closer the ABI is to 1.0, the more balanced the blood pressure in the ankle and arm, indicating generally better arterial circulation.

ABI from 1.0 to 1.4: Normal

This is considered the ideal range for most adults.

• Blood flow to the legs is relatively good.
• Lower limb arteries show no significant signs of occlusion.
• The risk of developing peripheral arterial disease is low.

Typically, the closer the result is to 1.0, the more it reflects the balance between arm and ankle blood pressure.

ABI from 0.91 to 1.30: Generally normal blood vessels

This level is still considered within the normal range.

• The arterial system typically has no severe damage.
• Blood flow to the legs is relatively well-maintained.
• Some individuals with an index from 0.91 to 0.99 may still experience leg pain or discomfort during strenuous activity.

If unusual symptoms occur despite a near-normal ABI, consult a doctor for a comprehensive evaluation.

ABI from 0.41 to 0.90: Mild to moderate peripheral arterial disease

This result indicates that blood flow to the legs may be restricted.

• There is a risk of lower limb arterial stenosis or atherosclerosis.
• Calf pain may occur when walking, leg numbness, or a cold sensation in the feet.
• Further in-depth examination is usually required to determine the extent of the damage.

The doctor may order additional imaging diagnostics such as angiography or other specialized tests.

ABI below 0.40: Severe peripheral arterial disease

This is a high-risk warning level.

• Blood flow to the legs is severely reduced.
• Increased risk of developing difficult-to-heal ulcers on the feet or lower legs.
• Can lead to tissue necrosis if not treated promptly.

Patients require early medical evaluation to limit dangerous complications.

ABI above 1.30: Calcified or incompressible arteries

An excessively high result does not mean healthy blood vessels.

• The artery wall may calcify and lose elasticity.
• Measured blood pressure may be falsely elevated.
• The ABI in this case may not accurately reflect actual blood circulation.

This condition is common in people with long-standing diabetes, chronic kidney disease, or other conditions that cause vascular calcification.

When should you see a doctor?

You should consult your doctor if:

• Your ABI is below 0.90 or above 1.30.
• You experience leg pain when walking or exercising.
• You have numbness, cold feet, or slow-healing wounds on your feet.
• You have a history of diabetes, high blood pressure, dyslipidemia, or prolonged smoking.

Monitoring and correctly interpreting the ankle-brachial index (ABI) helps in early detection of peripheral artery disease, assessing the risk of vascular occlusion, and preventing severe cardiovascular complications in the future.

Important Notes When Measuring ABI

Recognizing Signs of Peripheral Artery Disease

Measuring the ankle-brachial index (ABI) is particularly useful when patients show symptoms related to reduced blood flow in the legs.

• Calf pain when walking or exercising.
• Leg pain that subsides with rest.
• Slow-healing ulcers on the feet, toes, or lower legs.
• Abnormal skin discoloration on the legs, pale or bluish.
• Thinning or significant loss of leg hair.
• Leg skin that is cold, clammy, or less elastic than normal.

These could be warning signs of peripheral artery disease, lower extremity arterial stenosis, or atherosclerosis.

Who Should Get Regular ABI Checks?

Even without obvious symptoms, some individuals are at high risk for peripheral vascular disease and should be screened early.

• Long-term smokers.
• Diabetics aged 50 or older.
• Individuals with a family history of cardiovascular disease or stroke.
• Individuals with dyslipidemia or high cholesterol.
• Individuals with prolonged hypertension.
• Individuals with a history of cardiovascular disease.

Regular ABI measurements help detect vascular damage early before serious complications arise.

Assessing Overall Health Before Measurement

The results of an ABI measurement can be affected by many different health factors.

• Some vascular diseases can skew measurement results.
• Artery calcification can cause a falsely elevated ABI.
• Chronic diseases like diabetes or kidney disease can affect the accuracy of the measurement.

Therefore, a comprehensive review of the patient's medical history and current health status is necessary when interpreting the results.

Do Not Self-Measure Unless Trained

Although ABI measurement is a non-invasive technique, performing the procedure correctly requires specialized knowledge and skills.

• Knowing how to use a blood pressure cuff and Doppler probe is essential.
• Accurately locating arteries in the arm and ankle is necessary.
• Understanding how to record and calculate results is crucial.

If you are not trained or do not have the necessary specialized equipment, it is advisable to have the check performed at a medical facility to obtain the most accurate and reliable ABI measurement results.

Role of ABI in Vascular Disease Screening

ABI is one of the simple yet effective methods for assessing arterial system health.

• Aids in early detection of peripheral artery disease.
• Evaluates the risk of vascular occlusion in the legs.
• Supports monitoring the progression of atherosclerosis.
• Contributes to predicting the risk of future cardiovascular events.

Timely ABI checks can help detect disease in its early stages, thereby improving treatment effectiveness and reducing the risk of dangerous complications.

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Content edited by: Leigh Kennedy Ly.

Information consulted and verified by expert: Charlotte Davis.