From the Guidelines
The normal range for the Ankle-Brachial Index (ABI) is between 1.00 and 1.40, as indicated by the 2016 AHA/ACC guideline on the management of patients with lower extremity peripheral artery disease 1. This range is crucial in diagnosing and assessing the severity of peripheral arterial disease (PAD).
- An ABI between 1.00 and 1.40 suggests healthy blood flow to the legs.
- An ABI of 0.91 to 0.99 is considered borderline, while an ABI of 0.71 to 0.90 indicates mild PAD.
- Values above 1.4 typically suggest calcified, non-compressible arteries, often seen in patients with diabetes or kidney disease, and may require alternative diagnostic methods such as the toe-brachial index (TBI) 1. When interpreting ABI results, it's essential to consider both legs, as differences between limbs can provide valuable diagnostic information.
- The test is performed by measuring systolic blood pressure at both arms and ankles, then dividing the ankle pressure by the higher arm pressure.
- ABI measurements help clinicians determine appropriate treatment strategies, from lifestyle modifications for mild disease to potential surgical interventions for severe cases, as outlined in the 2016 AHA/ACC guideline 1.
From the Research
Ankle-Brachial Index (ABI) Ranges
The normal range for the Ankle-Brachial Index (ABI) is generally considered to be between 0.9 and 1.4 2.
- An ABI less than 0.9 is often used as an indicator of peripheral arterial disease (PAD) 3, 2.
- An ABI greater than 1.4 may also be considered abnormal, as it can indicate non-compressible arteries 4.
- Some studies have used a cutoff of less than 0.99 to define an abnormal ABI 5.
ABI Interpretation
It's essential to note that ABI values should be interpreted in the context of clinical symptoms and other diagnostic tests 6, 4.
- A normal ABI does not necessarily rule out PAD, as some patients with PAD may have a normal ABI 6.
- An abnormal ABI can be associated with an increased risk of cardiovascular events and mortality, even in asymptomatic individuals 2, 4.
Clinical Implications
The measurement of ABI is a useful tool for identifying individuals at risk of cardiovascular disease and PAD 3, 2.
- ABI screening can help identify asymptomatic individuals with PAD, allowing for early intervention and potentially reducing the risk of cardiovascular events 2.
- The prevalence of abnormal ABI varies depending on the population being studied, with higher rates found in older adults and those with significant coronary artery disease 3, 4.