Normal Ankle-Brachial Index (ABI) Ranges
According to the 2024 ESC Guidelines, the normal ABI range is 1.00-1.40, with values ≤0.90 considered abnormal (indicating peripheral arterial disease), values between 0.91-0.99 considered borderline, and values >1.40 indicating non-compressible arteries. 1
Understanding ABI Ranges
The Ankle-Brachial Index is a critical diagnostic tool for assessing peripheral arterial disease (PAD). The ranges are clearly defined in multiple guidelines:
Standard ABI Classification:
- Normal ABI: 1.00-1.40
- Borderline ABI: 0.91-0.99
- Abnormal ABI (indicating PAD): ≤0.90
- Non-compressible arteries: >1.40
This classification is consistently supported by both European and American guidelines, including the 2011 ACCF/AHA focused update which explicitly recommends that "ABI results should be uniformly reported with noncompressible values defined as greater than 1.40, normal values 1.00 to 1.40, borderline 0.91 to 0.99, and abnormal 0.90 or less." 1
Clinical Significance of Different ABI Values
ABI ≤0.90
- Confirms the diagnosis of peripheral arterial disease (PAD)
- Has 68%-84% sensitivity and 84%-99% specificity for PAD diagnosis 1
- Associated with approximately 4-fold higher risk of critical limb ischemia and ischemic leg amputation compared to normal values 2
- Indicates increased risk of cardiovascular mortality (odds ratio 3.23) 3
Borderline ABI (0.91-0.99)
- Requires further diagnostic evaluation, particularly in symptomatic patients
- Associated with 1.7-2.0 times higher risk of severe ischemic leg outcomes compared to normal values 2
- Should prompt consideration of post-exercise ABI testing to unmask moderate stenosis 1
Normal ABI (1.00-1.40)
- Indicates absence of significant PAD
- However, in symptomatic patients with normal resting ABI, exercise testing with post-exercise ABI is recommended to rule out PAD 1
ABI >1.40
- Indicates non-compressible vessels due to medial calcification
- Common in patients with diabetes mellitus or advanced age
- Alternative tests should be used, including:
- Toe-brachial index (TBI)
- Doppler waveform analysis
- Pulse volume recording 1
Measurement Considerations
For accurate ABI measurement:
- Patient should be in supine position
- 5-10 minutes of rest before measurement
- Maintain constant room temperature
- Use appropriately sized cuffs on upper arms and lower limbs (just above the ankle)
- For TBI measurement, use photoplethysmography probe on distal pulp of first or second toe 1
Special Populations
Diabetic Patients
- ABI may be less sensitive in diabetic patients due to medial calcification
- Consider using toe-brachial index (TBI) with normal value defined as ≥0.70 1
- Clairotte et al. suggested slightly higher ABI cutoff values (1.00-1.04) may be appropriate for diabetic patients 1
Elderly Patients
- Higher prevalence of non-compressible vessels
- Lower sensitivity of standard ABI measurement
- Consider alternative tests like TBI when ABI >1.40 4
Clinical Pitfalls to Avoid
Don't rely solely on ABI in patients with non-compressible vessels - In patients with diabetes or advanced age, use toe-brachial index or other alternative methods when ABI >1.40
Don't dismiss borderline ABI values (0.91-0.99) - These values are associated with increased risk of adverse outcomes and may warrant further investigation, especially in symptomatic patients
Don't overlook normal ABI in symptomatic patients - Exercise testing with post-exercise ABI should be performed in patients with exertional symptoms and normal resting ABI
Don't use incorrect measurement technique - Proper patient positioning, rest period, and cuff placement are essential for accurate results
Don't ignore the prognostic value of ABI - Beyond diagnosis, ABI provides important information about cardiovascular risk and should be considered in overall risk assessment
By understanding these ABI ranges and their clinical implications, clinicians can better diagnose PAD and assess cardiovascular risk, leading to improved patient outcomes through appropriate management strategies.