Toe-Brachial Index (TBI) Assessment

The ankle – brachial pressure index (ABI) is a simple, useful method for diagnosing Peripheral

Arterial Disease (PAD). In determining the severity of PAD in a lower extremity, the toe-brachial
index (TBI) is used.

Due to both lifestyle and genetic reasons, arteries may become hardened. This atherosclerotic
condition may not cause painful symptoms until the artery is narrowed 60% or more. A blood
clot or piece of cholesterol or calcium that may break off and move into the artery could cause
a blockage that would disrupt blood flow. The legs are the area of the body most commonly
damaged by PAD.

Severe PAD may lead to Critical Limb Ischemia, where blockages have become so severe that
legs and feet are no longer receiving blood flow.

The degree of PAD depends on when it is diagnosed and other present risk factors such as
smoking, high cholesterol, heart disease and diabetes.

The Toe-Brachial Index (TBI) Process

The test is performed using a photoplethysmograph (PPG) infrared light sensor on the left
finger and the right toe, while the patient is in a reclining position. The resultant Toe-Brachial
Index (TBI) is generated using readings from the finger and toe. A TBI reading is done for each
leg. 0.75 TBI is considered normal.