Ankle–brachial pressure index (ABPI)
What it means
Ratio of ankle to brachial systolic BP. 0.9–1.3 = normal; 0.5–0.9 = peripheral arterial disease (intermittent claudication); <0.5 = critical limb ischaemia (rest pain, tissue loss); >1.3 = incompressible/calcified vessels (diabetes, CKD — falsely high, unreliable). Venous-ulcer compression bandaging needs an ABPI ≥0.8 first.
Worked example
A diabetic with a deep punched-out heel ulcer and ABPI 0.68 → the ulcer is ARTERIAL, not neuropathic (which has a NORMAL ABPI with reduced sensation).
In the exam
A man with a heel ulcer has reduced vibration sense but normal light touch and an ankle–brachial pressure index of 0.68.
What settles it
ABPI <0.9 = arterial disease, <0.5 = critical ischaemia, >1.3 = calcified/unreliable. Neuropathic ulcers keep a NORMAL ABPI with sensory loss.
Source: NICE CKS — Peripheral arterial disease