The assessment of the diabetic foot is fundamentally aimed at identifying patients at risk of ulceration, infection, and amputation before tissue breakdown occurs. Neuropathy is central to that process, because loss of protective sensation, impaired autonomic function, and altered biomechanics all increase plantar loading and reduce the foot’s ability to defend itself. Neuropad has attracted interest because it offers a simple bedside method of detecting one important component of diabetic neuropathy: sudomotor dysfunction. By measuring the skin’s ability to change colour in response to sweat, it provides an indirect marker of sympathetic cholinergic small-fibre function.
Neuropad is applied to the plantar surface of the foot, typically over the great toe or forefoot region, and the result is read after a set period according to the degree and speed of colour change from blue to pink. In healthy skin, the plaster changes colour relatively quickly because sweating is intact. When the colour change is delayed, incomplete, or absent, this suggests reduced sweating and therefore autonomic neuropathy. This mechanism is clinically relevant because autonomic neuropathy contributes to dry, brittle skin and higher vulnerability to cracking and ulceration, especially in patients with diabetes who already have pressure-related risk factors.
The main strength of Neuropad is practicality. It is non-invasive, easy to perform, inexpensive, and does not require advanced equipment or specialised neurophysiology training. These features make it attractive in primary care, podiatry, and other outpatient settings where rapid risk stratification is needed. A meta-analysis of 18 diagnostic studies involving 3470 participants found average sensitivity of 86% and specificity of 65%, supporting its role as a triage test that can help rule out the “foot at risk” when negative. The same review concluded that patients with a positive result should be referred for more specialised assessment to establish a definite diagnosis.
A further advantage is that Neuropad appears to assess small-fibre dysfunction relatively well. In a comparative study of diabetic patients, its accuracy was stronger against corneal nerve fibre length, a marker of small-fibre damage, than against traditional large-fibre tests such as neuropathy disability score, vibration perception threshold, and motor nerve conduction velocity. This matters because early diabetic neuropathy often involves small fibres first, including autonomic fibres, before conventional bedside tests become clearly abnormal. In that sense, Neuropad may detect an earlier stage of neuropathic change than routine large-fibre-focused screening alone.
There is also evidence linking Neuropad to clinical ulcer risk. In one study of type 2 diabetes, the time to complete colour change performed better than 10 g monofilament testing in predicting diabetic foot ulcer risk, with an area under the ROC curve of about 0.8 and a suggested cut-off around 22.25 minutes. This supports the idea that sudomotor impairment is not merely a laboratory marker but has practical value in identifying patients more likely to develop foot complications. Another study in patients with diabetic foot ulceration found that Neuropad was a reliable and easy-to-use test for autonomic neuropathy, which was associated with greater ulceration and amputation risk.
However, Neuropad has important limitations. Its specificity is only moderate, so a positive result does not confirm neuropathy on its own and may produce false positives. It should therefore be interpreted within a full diabetic foot assessment that includes history, inspection, vascular assessment, monofilament or other sensory testing, footwear review, and biomechanical evaluation. The test also does not replace formal neurological examination, and the evidence base has been criticised for risk of bias and uncertainty about patient-important outcomes such as ulcer prevention, cost-effectiveness, and impact on long-term management. For these reasons, Neuropad is best viewed as an adjunctive screening tool rather than a definitive diagnostic test.
In clinical practice, the most defensible use of Neuropad is as part of a layered risk-assessment strategy. A negative result can add reassurance when the overall clinical picture suggests low risk, while an abnormal result can strengthen the case for closer surveillance, patient education, pressure management, and referral for comprehensive neuropathy evaluation. In a podiatry or diabetes clinic, this may be especially useful where there is concern about early autonomic involvement, dry skin, recurrent callus, or unexplained fissuring, all of which can precede ulceration. Its simplicity also makes it attractive for self-testing and community-based screening, although that should not substitute for professional foot surveillance.
Overall, Neuropad has a clear place in the assessment of the diabetic foot as a simple indicator of sudomotor dysfunction and small-fibre neuropathy. Its best role is as a screening or triage tool that helps identify patients needing more detailed evaluation, rather than as a standalone diagnostic endpoint. In an era where diabetic foot complications remain a major cause of morbidity, a test that is quick, non-invasive, and reasonably sensitive can be clinically valuable if used appropriately within a broader assessment framework.[