Diabetic peripheral neuropathy affects up to 50% of people with diabetes, and small?fibre neuropathy is often the earliest manifestation. Small fibres are responsible for pain perception and autonomic functions, including sweat production. Sudomotor dysfunction leads to dry, cracked skin, which increases susceptibility to fissures, infection, ulceration, and ultimately amputation. In England alone, around 6,000 lower?limb amputations were recorded in 2014–15 due to diabetic neuropathy and its complications.

Current guidelines recommend annual foot screening for all adults with diabetes, with more frequent assessments for those at increased risk. However, many patients do not receive regular checks, and traditional tests may miss early small?fibre damage. This gap highlights the need for accessible, sensitive tools that can detect neuropathy before irreversible complications develop.

What Is the Neuropad?

The Neuropad (TRIGOcare International) is a point?of?care diagnostic patch that assesses sudomotor function. It consists of a small adhesive plaster containing cobalt chloride, a chemical that changes colour in response to moisture. When applied to the plantar surface of the foot, the patch reacts to sweat production:

• Blue ? Pink: normal sweat production; low risk of neuropathy
• Partial colour change: impaired sudomotor function
• Remains blue: significant sudomotor dysfunction, suggestive of small?fibre neuropathy

The test takes approximately 10 minutes, requires no patient response, and can be performed by clinicians or used as a self?test at home. This makes it particularly useful for individuals with communication difficulties, cognitive impairment, or limited access to regular foot care services.

Mechanism of Action: Assessing Sudomotor Function

Sudomotor function is mediated by the sympathetic cholinergic fibres of the autonomic nervous system. Damage to these fibres is one of the earliest signs of diabetic neuropathy. Reduced sweating leads to dry, fragile skin, which is prone to breakdown.

The Neuropad assesses this function by detecting moisture levels on the skin surface. Because small?fibre neuropathy often precedes large?fibre involvement, the Neuropad may identify neuropathy before abnormalities appear on monofilament or vibration tests. This early detection is crucial for preventing ulceration.

Evidence Base and Diagnostic Accuracy

The NICE Medical Technologies Evaluation Programme reviewed the Neuropad and identified 18 relevant studies, most of which assessed diagnostic accuracy against reference standards such as the Neuropathy Disability Score (NDS)

Key findings from the evidence:

• Neuropad shows high sensitivity for detecting small?fibre neuropathy.
• It is less specific than some large?fibre tests, meaning it is best used as part of a multimodal assessment.
• One longitudinal study demonstrated that an abnormal Neuropad result was associated with a higher risk of future foot ulceration, supporting its prognostic value.
• The test is reproducible, easy to administer, and well?tolerated.

Although the evidence base is largely observational, the consistency of findings across multiple prospective studies supports the Neuropad’s clinical utility.

Clinical Applications in Diabetic Foot Assessment

Early Detection of Neuropathy

Because the Neuropad detects small?fibre dysfunction, it can identify neuropathy earlier than traditional sensory tests. This allows clinicians to intervene sooner with:

• Patient education
• Emollient therapy for dry skin
• Footwear modification
• Increased monitoring frequency
• Referral to podiatry or multidisciplinary foot services

Risk Stratification

NICE guidelines classify patients as low, moderate, or high risk based on neuropathy, pulses, deformity, and history of ulceration. The Neuropad can enhance this process by providing an objective measure of autonomic dysfunction.

Self?Monitoring

One of the Neuropad’s most significant advantages is its suitability for home use. Patients can perform the test regularly, enabling early detection of deterioration between annual clinical reviews. This is particularly valuable in rural or underserved areas where access to podiatry services may be limited.

Use in Special Populations

The Neuropad is especially useful for:

• People with communication difficulties
• Individuals with dementia
• Patients unable to reliably respond to sensory testing
• Community settings where specialist equipment is unavailable

Advantages of the Neuropad

Non?Invasive and Easy to Use

The test requires no specialised training and can be performed by any healthcare professional or by patients themselves.

Objective and Visual

The colour change provides a clear, visual indicator that reduces subjectivity in interpretation.

Early Detection of Small?Fibre Neuropathy

This is a major advantage over monofilament testing, which detects later?stage large?fibre loss.

Cost?Effective

The Neuropad is inexpensive compared with nerve conduction studies, corneal confocal microscopy, or quantitative sudomotor axon reflex testing (QSART).

Complements Existing Tests

It is not intended to replace monofilament testing but to augment current screening pathways.

Limitations and Considerations

Despite its benefits, the Neuropad has limitations:

• Lower specificity means false positives may occur.
• Environmental factors (e.g., cold feet) may affect sweat production.
• It does not assess large?fibre function, so it must be used alongside other tests.
• Evidence, while promising, includes few large randomized trials.

NICE concluded that while the Neuropad shows potential, more research is needed to fully establish its role in routine screening.

Integration into Clinical Practice

The Neuropad fits well within modern diabetic foot care models, which emphasise:

• Early detection
• Patient empowerment
• Multidisciplinary management
• Prevention of ulceration and amputation

In practice, the Neuropad can be incorporated into annual foot checks or used more frequently in high?risk individuals. Its ability to detect early sudomotor dysfunction makes it a valuable adjunct to existing tools.

The Neuropad represents an innovative, accessible, and patient?friendly method for assessing sudomotor function and detecting early diabetic peripheral neuropathy. By identifying small?fibre dysfunction before traditional tests reveal abnormalities, it offers an opportunity for earlier intervention and improved prevention of diabetic foot complications. Although further research is warranted to refine its diagnostic accuracy and long?term impact, current evidence supports its use as part of a comprehensive diabetic foot assessment strategy. As diabetes prevalence continues to rise, tools like the Neuropad will play an increasingly important role in reducing the burden of foot disease and preventing avoidable amputations.