What Is a Toe-Brachial Index (TBI) Test?
A Toe-Brachial Index (TBI) is a noninvasive vascular examination that measures blood flow to your feet by comparing the blood pressure in your big toe with the blood pressure in your arm. The resulting ratio helps evaluate circulation and detect Peripheral Arterial Disease (PAD), particularly in patients whose arteries may be difficult to assess with a standard Ankle-Brachial Index (ABI).
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A TBI is especially useful for individuals with diabetes, chronic kidney disease, or advanced age, as the arteries at the ankle can become stiff or calcified, making ABI measurements less reliable. Because the arteries in the toes are much less likely to become calcified, the TBI often provides a more accurate assessment of blood flow to the lower extremities.
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The examination is performed using a small blood pressure cuff placed around the base of the big toe and a photoplethysmography (PPG) sensor attached to the toe to detect blood flow. The test is painless, involves no needles or radiation, and typically takes 15–30 minutes to complete.
Calculation Formula
TBI = Toe Systolic Pressure ÷ Highest Brachial Systolic Pressure
How It Works
Why Is a Toe-Brachial Index (TBI) Evaluation?
A Toe-Brachial Index (TBI) is performed to evaluate blood flow to the feet and help detect Peripheral Arterial Disease (PAD). This examination is especially useful when a standard Ankle-Brachial Index (ABI) may not provide reliable results due to stiff or calcified arteries at the ankle.
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A TBI is commonly recommended for patients with diabetes, chronic kidney disease, advanced age, or other conditions that can cause arterial calcification. Because the arteries in the toes are much less likely to become calcified, the TBI often provides a more accurate assessment of blood flow to the lower extremities.
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A TBI can help identify reduced circulation, assess the severity of peripheral arterial disease, evaluate wound-healing potential, and guide treatment decisions. It is also frequently used alongside an ABI to provide a more complete evaluation of lower extremity circulation.
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Unlike many other vascular examinations, a TBI is particularly valuable for detecting circulation problems in patients whose ABI appears normal or falsely elevated due to noncompressible ankle arteries.
Common Reasons to Schedule a Toe-Brachial Index (TBI) Evaluation
A Toe-Brachial Index (TBI) Evaluation measures the blood pressure in your big toe and compares it to the blood pressure in your arm. This noninvasive physiologic vascular test helps evaluate blood flow to the feet and is especially useful when an Ankle-Brachial Index (ABI) may be unreliable due to hardened or calcified arteries. You may benefit from this examination if you have symptoms or medical conditions that suggest reduced circulation to your feet or toes.
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Leg pain while walking (claudication)
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Pain in the feet or toes at rest
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Cold feet or toes
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Numbness or tingling related to poor circulation
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Slow-healing wounds or ulcers on the feet or toes
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Non-healing sores or gangrene of the toes
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Suspected peripheral arterial disease (PAD)
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Diabetes with concern for reduced circulation
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Chronic kidney disease or dialysis, where calcified arteries may make ABI measurements less reliable
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Evaluation of circulation before wound care or limb salvage procedures
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Assessment before or after vascular surgery, angioplasty, or stent placement
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Monitoring previously diagnosed peripheral arterial disease
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Weak or absent pulses in the feet
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Evaluation of abnormal findings from a physical examination or another vascular study
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A Toe-Brachial Index (TBI) Evaluation provides an accurate assessment of blood flow to the feet and toes, particularly in individuals with diabetes, kidney disease, or calcified leg arteries. It is a safe, painless, noninvasive, and radiation-free examination that helps detect peripheral arterial disease, determine the severity of reduced circulation, and guide appropriate diagnosis, treatment, and follow-up care.
What to Expect During Your Examination
A Toe-Brachial Index (TBI) is a quick, noninvasive examination that typically takes 15–30 minutes to complete. You will lie comfortably on an examination table while blood pressure cuffs are placed around your arms and the base of each big toe.
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A small photoplethysmography (PPG) sensor will be attached to each big toe to detect blood flow. The blood pressure cuffs will gently inflate and deflate while pressure measurements are obtained from your arms and toes. These measurements are then used to calculate the Toe-Brachial Index for each foot.
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The examination is painless, although you may feel temporary pressure from the blood pressure cuffs. There are no needles, injections, or radiation, and most patients find the test comfortable and easy to tolerate.
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Once the examination is complete, you may resume your normal daily activities immediately. Your results will be reviewed by a physician and used to evaluate blood flow to your feet and help determine whether additional testing or treatment is recommended.
How to Prepare for Your Toe-Brachial Index (TBI) Evaluation
A Toe-Brachial Index (TBI) Evaluation requires very little preparation. Following these simple instructions will help ensure your examination is completed comfortably and accurately.
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Before Your Appointment
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✓ No fasting is required. You may eat and drink normally before your examination.
✓ Continue taking your prescribed medications unless instructed otherwise by your healthcare provider.
✓ Avoid smoking, chewing tobacco, vaping, or using nicotine products for at least 2 hours before your appointment, as nicotine can temporarily reduce blood flow to your feet and toes and affect the accuracy of the examination.
✓ Avoid caffeine for at least 2 hours before your examination, including coffee, tea, energy drinks, and caffeinated sodas, as caffeine may temporarily affect blood vessel function.
✓ Wear comfortable, loose-fitting clothing that allows easy access to your legs and feet. You will be asked to remove your shoes and socks before the examination.
✓ Keep your feet warm before your appointment whenever possible, especially during colder weather, as cold temperatures can temporarily reduce blood flow to the toes.
✓ Bring any previous vascular ultrasound, physiologic testing, CT angiography (CTA), MR angiography (MRA), or angiogram reports related to your leg circulation if they were performed at another facility.
✓ Arrive 10–15 minutes early to complete any necessary paperwork before your examination.
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A Toe-Brachial Index (TBI) Evaluation is a safe, painless, noninvasive, and radiation-free examination that does not require contrast dye or injections. During the study, blood pressure cuffs are placed on your arm and ankle, and a small cuff with a specialized sensor is placed on your big toe to measure blood flow and toe pressure. Following these instructions will help ensure the most accurate and reliable results.
Frequently Asked Questions
Q: What is a Toe-Brachial Index (TBI)?
A: A Toe-Brachial Index (TBI) is a noninvasive examination that compares the blood pressure in your big toe with the blood pressure in your arm. It helps evaluate blood flow to your feet and detect Peripheral Arterial Disease (PAD).
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Q: Why would I need a TBI instead of an ABI?
A: A TBI is often recommended when an Ankle-Brachial Index (ABI) may not provide reliable results due to stiff or calcified arteries. This is common in patients with diabetes, chronic kidney disease, or advanced age.
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Q: Is the examination painful?
A: No. The examination is generally painless. You may feel temporary pressure as the blood pressure cuffs inflate, but most patients find the test comfortable.
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Q: How long does the examination take?
A: Most Toe-Brachial Index (TBI) examinations take approximately 15 to 30 minutes to complete.
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Q: Do I need to fast before my appointment?
A: No. You may eat and drink normally unless you have been given different instructions.
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Q: Is there any radiation exposure?
A: No. A TBI uses blood pressure cuffs and a photoplethysmography (PPG) sensor to evaluate circulation. There is no radiation exposure.
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Q: Will both feet be tested?
A: Yes. The examination is typically performed on both feet, allowing circulation to be evaluated separately for the right and left sides.
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Q: Can I return to my normal activities afterward?
A: Yes. You may resume your normal daily activities immediately after the examination.
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Q: Do I need a referral for this examination?
A: No. You do not need a referral if you are scheduling the examination as a self-pay patient. If you plan to use insurance, your insurance provider may require a referral or prior authorization. Our office can help verify your coverage and answer any questions before your appointment.
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Q: When will I receive my results?
A: A board-certified physician will interpret your examination, and the results will be sent to your referring healthcare provider. If you are a self-pay patient, we will explain how and when your results will be provided.
Schedule Your Toe-Brachial Index (TBI) Evaluation
Whether recommended by your healthcare provider or scheduled as a self-pay evaluation, a Toe-Brachial Index (TBI) provides a precise assessment of blood flow to your feet. This examination is especially valuable for patients with diabetes, chronic kidney disease, calcified arteries, or symptoms of poor circulation, where a standard Ankle-Brachial Index (ABI) may not provide reliable results.
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When scheduling your appointment, simply select Toe-Brachial Index (TBI) from our online booking system. If you have had previous vascular testing, angioplasty, stent placement, bypass surgery, or are being evaluated for a foot wound or ulcer, please let us know when scheduling or bring any relevant medical records to your appointment.
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We look forward to providing you with a comprehensive vascular assessment in a comfortable, professional setting and helping you better understand your vascular health.
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If you are experiencing sudden severe foot or leg pain, a cold or pale foot, loss of sensation, an inability to move your toes, or rapidly worsening foot wounds, seek immediate medical attention rather than scheduling a routine examination, as these symptoms may require emergency evaluation.
Why Choose Alpha Vascular?
Experienced Sonographer
Board-Certified Interpretation
Advanced Ultrasound Technology
