Normal Ankle-Brachial Index (ABI) Results
A normal ABI ranges from 0.91 to 1.40, with values between 1.11 and 1.40 representing the optimal range associated with the lowest cardiovascular risk. 1, 2
Understanding the Normal Range
The standard normal ABI range is 0.91 to 1.40, as established by the American Heart Association, indicating absence of significant peripheral arterial disease and lower cardiovascular risk compared to individuals with abnormal values. 1, 2
Values between 1.11 and 1.40 represent the optimal range where cardiovascular risk is lowest, based on the reverse J-shaped curve relationship between ABI and mortality. 2
Values between 0.91 and 1.00 are considered "borderline" and require clinical context for interpretation, as they may represent early or mild peripheral arterial disease. 1, 2
Clinical Significance of Normal Values
A normal ABI indicates adequate arterial blood flow to the lower extremities and suggests absence of significant atherosclerotic disease. 2
Normal ABI values correlate with lower risk of cardiovascular events and mortality compared to abnormal values. 2
Normal ABI does not completely exclude PAD in symptomatic patients, particularly those with exertional leg symptoms, as some patients may have normal resting ABI but abnormal post-exercise ABI. 1, 2
Abnormal Values for Context
ABI ≤0.90 indicates peripheral arterial disease and is associated with increased cardiovascular risk. 1, 3
ABI >1.40 suggests non-compressible arteries due to arterial calcification (commonly seen in diabetes and chronic kidney disease) and is also associated with increased cardiovascular events and mortality. 1, 2
Important Clinical Caveats
When clinical suspicion of PAD remains despite normal resting ABI (0.91-1.40), post-exercise ABI testing should be performed, as exercise can unmask moderate stenoses not apparent at rest. 1, 2, 4
In diabetic patients, a normal ABI may be falsely reassuring due to medial arterial calcification (Mönckeberg sclerosis), which can produce normal or elevated readings despite significant stenotic disease. In these patients, toe-brachial index (TBI) should be obtained. 2, 4
ABI should be measured in both limbs, as PAD may not progress symmetrically between legs. 1
Serial ABI measurements may be more accurate than a single measurement, particularly in research settings or when monitoring disease progression. 1
The optimal cutoff value of 0.90 should not be considered a strict binary marker—clinical judgment is essential when interpreting borderline values (0.91-1.00), especially in symptomatic patients. 1