When the ankle-brachial index test is complete, your doctor calculates your ankle-brachial index by dividing the systolic blood pressure (top number) at the arteries near your ankle by the systolic blood pressure in the arms. Compared to the arm, lower blood pressure in the leg is an indication of PAD.
Based on the number your doctor calculates, your ankle-brachial index may show you have:
- No blockage (1.0 to 1.4). An ankle-brachial index number in this range suggests that you probably don't have peripheral artery disease. But if you have certain risk factors, such as diabetes, smoking or a family history of PAD, tell your doctor so that he or she can continue to monitor your risk.
- Blockage (0.9 or less). An ankle-brachial index number less than 1.0 indicates narrowing of the arteries in your leg. Depending on how low the number is, blockage may range from mild to severe, indicating mild to severe PAD.
- Rigid arteries (more than 1.4). If your ankle-brachial index number is higher than 1.4, this may mean that your arteries are rigid and don't compress when the blood pressure cuff is inflated. You may need an ultrasound test to check for peripheral artery disease instead of an ankle-brachial index test, or a toe-brachial index test, in which the blood pressures in your arm and big toe are compared.
If you have an exercise ankle-brachial index test, the ranges for results differ. Talk to your doctor about what your results mean.
Depending on the severity of your blockage, your doctor may recommend lifestyle changes, medications or surgery to treat PAD. Talk to your doctor about your options. You may also need additional imaging tests to see what treatment is best for you.
The test may not adequately measure the ankle-brachial index if you have severe diabetes or calcified arteries with significant blockage. Instead, your doctor may need to read your blood pressure at your big toe (toe-brachial index) to get an accurate test result if you have either of these conditions.
Aug. 22, 2015
- What is peripheral arterial disease? National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/health-topics/topics/pad/#. Accessed July 23, 2015.
- Mohler ER, et al. Noninvasive diagnosis of arterial disease. http://www.uptodate.com/home. Accessed July 22, 2015.
- AskMayoExpert. How are the results of ankle-brachial index testing classified at Mayo Clinic? Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2015.
- Conte MS, et al. Society for Vascular Surgery practice guidelines for atherosclerotic occlusive disease of the lower extremities: Management of asymptomatic disease and claudication. Journal of Vascular Surgery. 2015;61:2S.
- Ankle brachial index: Quick reference guide for clinicians. Journal of Wound Ostomy and Continence Nursing. 2012;39:S21.
- Litin SC (expert opinion). Mayo Clinic, Rochester, Minn. July 24, 2015.
- Mankad R (expert opinion). Mayo Clinic, Rochester, Minn. Aug. 7, 2015.