Understanding the technology
About This Technology.
The ankle-brachial index (ABI) test measures blood pressure at your ankles and arms and compares the two. When the leg arteries are narrowed, the pressure at the ankle is lower than in the arm. Doctors use it to detect peripheral artery disease and gauge its severity. The test uses blood pressure cuffs, with no needles and no radiation.
What Is the Ankle-Brachial Index Test?
When blood flows normally, the blood pressure at your ankle is the same as or slightly higher than in your arm. If the leg arteries are narrowed by plaque, less pressure reaches the ankle. The ankle-brachial index (ABI) test uses this difference. Systolic pressure, the upper number in a blood pressure reading, is measured in both arms and both ankles. For each leg, the ankle pressure is divided by the higher arm pressure, and the result is called the index.
What the Numbers Mean
- 1.00 to 1.40: generally considered normal.
- 0.91 to 0.99: borderline, judged together with your symptoms and risk factors.
- 0.90 or lower: indicates peripheral artery disease; the lower the number, the more severe the narrowing.
- Above 1.40: the arteries are too stiff from calcium to be compressed by the cuff. This result cannot be used to judge narrowing, and your doctor may measure pressure at the toe instead (toe-brachial index).
Your doctor reads this number together with your symptoms, not as a diagnosis on its own.
When Your Doctor May Recommend It
Your doctor may suggest an ABI test if you have pain or cramping in your calf when walking that eases with rest (claudication), a foot wound that heals slowly, or weak pulses in your feet. It is also used to check people at higher risk, such as those with diabetes, smokers, or people who already have coronary artery disease, and to monitor results after a procedure on the leg arteries.
During the Test
You lie flat on your back and rest for a few minutes. Staff place blood pressure cuffs on your arms and ankles, then measure the pressure with a handheld Doppler probe or automatic sensors. You will only feel the cuffs tighten briefly, as with a regular blood pressure check.
Limitations and Next Steps
The ABI shows whether blood flow is reduced and by how much, but not exactly where the narrowing is. If the result is abnormal, your doctor may follow up with a Doppler vascular ultrasound to map the arteries, and then CT angiography or angiography if a procedure is being considered. In people with diabetes or chronic kidney disease, stiff arteries can make the result look normal even when a narrowing is present, so your doctor may add a toe measurement. Decisions about further tests and treatment rest with the doctor who examines you.
Clinical use
Uses and Benefits.
Whether this technology suits your condition is decided by a doctor after an evaluation.
- Detecting peripheral artery disease in the legs
- Gauging how severely the leg arteries are narrowed
- Checking calf pain when walking that eases with rest
- Checking people at risk, such as those with diabetes, smokers, or people with coronary artery disease
- Monitoring leg blood flow after angioplasty or bypass surgery
- Helping assess overall heart and blood vessel risk
Benefits for the Doctor's Assessment
Simple and Needle-Free
The test uses only blood pressure cuffs and a sensor on the skin. There is no puncture, contrast dye, or radiation, so it can be repeated for monitoring.
A Number That Is Easy to Compare
The index for each leg can be compared over time, for example before and after a procedure on the leg arteries.
Recommended by Guidelines as an Initial Test
The 2024 ESC and ACC/AHA guidelines recommend the ABI as an initial test when peripheral artery disease is suspected.
Also Reflects Heart Risk
A low ABI is linked to a higher risk of heart attack and stroke, so the result helps your doctor plan prevention.
Brief Technical Information
- Test type
- Noninvasive, no needles
- What is measured
- Systolic blood pressure in both arms and both ankles
- Result
- An index number for each leg
- Radiation
- None
- Test position
- Lying on your back after a short rest
- Service location
- Vascular Diagnostic and Therapeutic Center
