This is the kind of study that should make every clinician who manages the diabetic foot sit up a little straighter.
The DM PAD study — a prospective, multicentre diagnostic accuracy study across 16 NHS centres and 604 patients — just landed in Health Technology Assessment. Led by Burgess, Normahani, and colleagues at Imperial College London, it asks a deceptively simple question: how well do the bedside tests we use every day actually detect peripheral arterial disease in people with diabetes?
The answer, in a word: poorly.
Against a reference standard of CTA or MRA (573 scans completed), 39% of participants had confirmed PAD. Here are the sensitivities of the five routinely used bedside tests:
- Audible Doppler waveform: 36%
- ABPI: 41%
- Exercise ABPI: 41%
- Visual Doppler waveform: 42%
- Toe-brachial pressure index: 55%
Read those numbers again. The best-performing conventional test — TBPI — still missed nearly half of all confirmed PAD cases. None demonstrated an acceptable combination of sensitivity and specificity.
But there’s a bright spot. A sixth test — the Podiatry Ankle Duplex scan (PAD-Scan), a focused point-of-care duplex ultrasound of the distal anterior and posterior tibial arteries — achieved 89% sensitivity. And prior health economic modeling from the same group showed PAD-Scan to be the most cost-effective strategy, reducing amputations by 24% and cardiovascular deaths by 10% over five years.
It’s worth understanding what the PAD-Scan actually gives you at the bedside — and what it doesn’t. Unlike ABI or TBPI, the PAD-Scan does not produce a single numeric index. Instead, the clinician evaluates the Doppler spectral waveform shape at the ankle and classifies it as triphasic (normal), biphasic, or monophasic (abnormal). Loss of the triphasic pattern is the signal for upstream disease. It is a qualitative, pattern-based assessment — not a number. This is both its strength (it bypasses the calcification artifact that renders pressure-based indices unreliable in diabetes) and its current limitation (it is operator-dependent and subject to inter-observer variability). Normahani’s group has been working on a machine learning algorithm to automate waveform classification, which could eventually convert this qualitative read into a quantitative probability score — a potential advance that would make PAD-Scan far more scalable and reproducible.
This is a big deal — but not entirely a surprise. We’ve been tracking this group’s work for years. Back in 2023, we covered their TrEAD prognostic performance study, which showed that no single bedside test performed well enough in isolation as a prognostic marker for DFU healing — and that PAD-Scan was the only test to independently predict ulcer healing at 12 months. The DM PAD study now confirms the diagnostic side of the same story, at scale, with CTA/MRA as the reference standard.
And here’s where a little nuance matters. Using CTA/MRA as the reference standard is rigorous — it’s the gold standard for identifying structural arterial disease, and the DM PAD investigators should be commended for choosing it over duplex ultrasound, which most prior studies relied on and which is itself less reliable in the calcified distal vessels typical of diabetes. But CTA/MRA measures anatomy, not function. It tells you there is a 50% or greater stenosis. It does not tell you whether that stenosis will prevent a wound from healing. That’s a fundamentally different question — and it’s why the earlier TrEAD prognostic study is so important as a companion to this one. In that study, PAD-Scan was the only bedside test that independently predicted ulcer healing at 12 months. So the same tool that best detects the structural disease is also the one most associated with the functional outcome that matters most to our patients: whether their wound will heal.
We have known for decades that medial arterial calcification and neuropathy confound standard hemodynamic testing in diabetes. We’ve known that ABI is unreliable in this population. And yet these tests remain the clinical standard of care in most centers worldwide.
The implications are clear. Routine bedside tests should not be relied upon in isolation to rule out PAD in people with diabetes. The investigators rightly suggest that it may be necessary to bypass traditional bedside tests entirely in favor of more reliable imaging — full lower-limb duplex ultrasound or, where available, PAD-Scan as a first-line assessment.
The beauty of the PAD-Scan concept is task-shifting: a focused, learnable, rapid ultrasound protocol that puts vascular assessment capability into the hands of podiatrists and frontline diabetes clinicians — the people who actually see these feet first. The Imperial group has shown it can be taught in a 3-hour intensive simulation session with over 92% accuracy, and in a structured 8-week multicenter program, trainees achieved perfect agreement with vascular scientists. There is currently no publicly available training video for the technique — something that, frankly, would dramatically accelerate adoption, especially outside the UK.
We cannot preserve what we cannot perfuse. And we cannot perfuse what we cannot detect.
Burgess L, Normahani P, Norrie J, Tuck S, Graham C, Epstein DM, Kandiyil N, Saratzis A, Heatley F, Smith S, Khunti K, Wingfield D, Coward T, Hartshorne T, Ashwell S, Shalhoub J, Pigott E, Davies AH, Jaffer U; DM PAD Trial Investigators. “Diagnostic tools to establish the presence and severity of peripheral arterial disease in people with diabetes: a synopsis of the DM PAD prospective multicentre diagnostic accuracy study.” Health Technol Assess. 2026 Mar 18:1-22. doi:10.3310/GJUJ2819
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