Ankle–Brachial Index: Quick Reference Guide for Clinical Use
The Ankle–Brachial Index (ABI) is a simple, noninvasive test that compares the systolic blood pressure at the ankle with that at the arm. It is widely used to detect Peripheral Arterial Disease (PAD) and guide wound care decisions.
Why ABI matters:
- PAD Risk Screening – Detects impaired blood flow in patients at risk for lower extremity wounds.
- Compression Safety – Determines whether compression therapy can be safely applied.
- Referral Guidance – Helps clinicians identify patients needing vascular evaluation.
How ABI is measured:
- Measure systolic pressure in both brachial arteries.
- Measure systolic pressure in dorsalis pedis and posterior tibial arteries at each ankle.
- Use the formula: ABI = Higher ankle pressure ÷ Higher brachial pressure (calculate separately for each leg).
ABI Interpretation:
| ABI Value | Interpretation | Action |
|---|---|---|
| 1.0 – 1.4 | Normal | No action needed |
| 0.9 – 1.0 | Acceptable | Monitor |
| 0.8 – 0.9 | Mild PAD | Risk factor modification |
| 0.5 – 0.8 | Moderate PAD | Specialist referral; compression with caution |
| < 0.5 | Severe PAD | Urgent vascular referral |
| > 1.4 | Calcified vessels | Further vascular testing (e.g., TBI) |
Limitations: ABI may be less reliable in patients with calcified or noncompressible vessels (e.g., diabetes, renal disease, elderly). In these cases, consider Toe–Brachial Index (TBI) or other vascular testing.
Read the full article in the Journal of Wound, Ostomy, and Continence Nursing