Toe Brachial Index: 7 Essential Facts for Accurate PAD Assessment

The toe brachial index (TBI) is a non-invasive vascular measurement that compares the systolic blood pressure in the big toe to the systolic pressure in the arm. It is the most reliable office test for evaluating peripheral arterial disease (PAD) when the ankle-brachial index (ABI) is unreliable — most often in patients with diabetes, chronic kidney disease (CKD), or advanced age, whose calcified leg arteries can produce a falsely normal or elevated ABI. A toe brachial index of 0.70 or lower is considered abnormal and supports a diagnosis of PAD.

Because the small arteries in the toes are rarely affected by the medial calcification that distorts ankle readings, the TBI often returns a usable result in limbs where the ABI cannot be obtained.

For independent practices that already perform PAD testing, adding the toe brachial index closes a critical diagnostic gap: the patients most likely to have hidden vascular disease are precisely the patients in whom the ABI is least trustworthy. This guide explains what the TBI measures, when to use it, what the numbers mean, and how the test fits into a point-of-care diagnostic workflow.

What Is the Toe Brachial Index?

The toe brachial index is the ratio of the toe systolic pressure to the higher of the two brachial (arm) systolic pressures. It is a non-invasive, painless measurement that takes only a few minutes and requires no contrast, radiation, or needles. The test serves the same purpose as the ABI — identifying reduced arterial blood flow in the lower limbs — but it measures pressure at the digital arteries of the toe rather than at the ankle.

That difference matters. In healthy adults, the mean TBI falls in the range of roughly 0.84 to 0.98. The toe arteries lie distal to the tibial vessels that are prone to stiffening, so the index gives an honest reading of perfusion even when the arteries higher up the leg are too rigid to compress accurately.

When Should You Use the Toe Brachial Index Instead of the ABI?

You should use the toe brachial index whenever the ABI is unreliable. The clearest signal is a resting ABI above 1.40, which indicates non-compressible, calcified ankle arteries rather than healthy blood flow. According to the 2024 ACC/AHA multisociety guideline for lower-extremity PAD, toe pressure and the TBI with waveforms should be performed when the resting ABI is greater than 1.40 (non-compressible). A TBI of 0.70 or lower is then considered abnormal and allows a diagnosis of PAD in patients who have history or examination findings that suggest it.

Consider the test in any of these situations:

• ABI above 1.40 — the hallmark of incompressible, medially calcified arteries.
• Diabetes mellitus — medial arterial calcification is common and frequently falsifies the ankle reading.
• Chronic kidney disease — especially in dialysis patients, where vascular calcification is widespread.
• Advanced age — arterial stiffening increases with age.
• A normal ABI with strong clinical suspicion of PAD — the TBI can unmask disease the ankle reading misses.

What Is a Normal Toe Brachial Index?

A toe brachial index above 0.70 is generally regarded as normal, while a value of 0.70 or below is considered abnormal and indicative of PAD. As the index falls, the severity of arterial insufficiency rises. The following ranges reflect commonly cited interpretive thresholds:

Absolute toe pressure is also clinically meaningful. A toe pressure below 30 mmHg is widely used as a marker of severe ischemia and supports chronic limb-threatening ischemia (CLTI) in the appropriate context, while international guidelines cite a cut-off in the 30–50 mmHg range as a threshold for impaired wound healing. A toe pressure of 30 mmHg or higher increases the likelihood that a foot wound will heal. Reporting both the index and the absolute toe pressure gives the fullest picture of perfusion.

How Is the Toe Brachial Index Measured?

The toe brachial index is measured with a small digital cuff placed around the base of the great toe and a photoplethysmography (PPG) sensor positioned distally on the toe. The patient rests supine with the feet level with the heart. The toe cuff is inflated until the PPG pulse signal disappears, then gradually deflated until the pulsatile signal returns — that point marks the toe systolic pressure. Dividing the toe pressure by the higher brachial systolic pressure yields the TBI.

Because the technique relies on an optical sensor rather than a hand-held Doppler at the ankle, it is reproducible and well suited to staff-operated, point-of-care testing. A complete physiologic study can pair the TBI with the ABI and pulse-volume recordings in a single visit.

Why Is the Toe Brachial Index Important for Diabetic and CKD Patients?

In diabetes and chronic kidney disease, the tibial arteries at the ankle frequently develop medial calcification that makes them resistant to compression. This produces a falsely elevated ABI — sometimes above 1.40 — even when significant PAD is present and confirmed on imaging. A clinician relying on the ankle reading alone may reassure a patient who in fact has advanced disease.

The toe brachial index sidesteps this problem because the digital arteries are rarely calcified, so they compress normally and report true perfusion.

This is why the TBI is the more informative study in patients with type 2 diabetes whose ankle readings cannot be trusted. Pairing it with autonomic nervous system testing, which documents the nerve dysfunction that can accompany diabetic vascular disease, gives independent practices a far more complete view of a high-risk patient than an ankle reading alone.

Toe Brachial Index vs ABI: What Is the Difference?

The ABI is the standard first test for PAD and works well in most patients. The TBI is the essential complement that takes over when the ABI cannot be trusted. The two tests are most powerful when used together.

For a deeper look at ankle measurement and its limits, see our guides to normal ankle-brachial index values and in-office vascular testing for independent practices.

How Can Independent Practices Add Toe Brachial Index Testing?

Independent practices can add the toe brachial index through a point-of-care diagnostic system that performs a full physiologic study in the office. The CMAT Advantage System from HealthWright Technologies, built on FDA-cleared component devices, measures the TBI alongside the ABI, volume plethysmography, heart-rate variability, and sudomotor function in a single non-invasive session that takes about 7 to 10 minutes.

Noninvasive physiologic studies that include toe pressure and the TBI are reported under CPT code 93923 (complete bilateral study). For a detailed breakdown of coding and documentation, see our ABI CPT code 93923 billing guide. Adding the test helps a practice document vascular status accurately, support appropriate referrals, and build a structured in-office diagnostics program. To learn how the program works, visit our partnership page.

Related HealthWright resources

• What is an ABI test?
• Understanding a normal ankle-brachial index
• CMAT Advantage system overview
• Contact our team

Frequently Asked Questions About the Toe Brachial Index

What is a normal toe brachial index?

A toe brachial index above 0.70 is generally considered normal, and healthy adults typically fall in the 0.84 to 0.98 range. A value of 0.70 or below is abnormal and supports a diagnosis of peripheral arterial disease, with lower values indicating more severe arterial insufficiency.

When is the toe brachial index used instead of the ABI?

The TBI is used when the ABI is unreliable, most notably when the resting ABI is above 1.40, which signals non-compressible calcified arteries. The 2024 ACC/AHA guideline recommends toe pressure and the TBI in this situation, which is common in patients with diabetes or chronic kidney disease.

How is the toe brachial index measured?

A small cuff is placed around the great toe and a photoplethysmography sensor is positioned on the toe while the patient lies supine. The cuff is inflated until the pulse signal disappears, then deflated until it returns to determine the toe systolic pressure, which is divided by the higher arm systolic pressure to calculate the index.

Why is the toe brachial index better for diabetic patients?

Diabetes often causes medial calcification of the ankle arteries, which falsely elevates the ABI and can mask real disease. The digital arteries in the toes rarely calcify, so the test provides an accurate reading of blood flow even when the ankle measurement cannot be trusted.

Can medical staff perform the test in the office?

Yes. Because automated systems such as the CMAT Advantage System use an optical sensor rather than operator-dependent Doppler at the ankle, trained clinical staff can perform the toe brachial index as part of a point-of-care physiologic study under physician supervision, with results available during the same visit.

Ready to add toe brachial index testing to your practice? Contact HealthWright Technologies to learn how the CMAT Advantage System brings comprehensive vascular and autonomic testing into your office, or request a demo.

HealthWright Technologies
60 Bear Creek Marina Road, Mansfield, GA 30055
Phone: (678) 322-7146
Email: contact@healthwrighttechnologies.com

Medical Disclaimer: This article is for general educational purposes for healthcare professionals and does not constitute medical or billing advice. Diagnostic thresholds and clinical decisions should be individualized to each patient. CPT codes are provided for reference only and do not guarantee reimbursement; verify coverage and code applicability with the relevant payer and your billing team. CPT is a registered trademark of the American Medical Association. The CMAT Advantage System is built on FDA-cleared component devices from LD Technology and is intended to measure physiologic parameters; it is not represented to diagnose, predict, or treat any specific disease.