The Neuropad test: a visual indicator test for human diabetic neuropathy

Abstract

Aims/hypothesis The commercially available Neuropad test was developed as a simple visual indicator test to evaluate diabetic neuropathy. It uses a colour change to define the integrity of skin sympathetic cholinergic innervation. We compared the results of Neuropad assessment in the foot with established measures of somatic and autonomic neuropathy. Methods Fifty-seven diabetic patients underwent Neuropad assessment, quantitative sensory and autonomic function testing, and evaluation of intra-epidermal nerve fibre density in foot skin biopsies. Results Neuropad responses correlated with the neuropathy disability score (r s =0.450, p<0.001), neuropathic symptom score (r s =0.288, p=0.03), cold detection threshold (r s = 0.394, p=0.003), heat-as-pain perception threshold visual analogue score 0.5 (r s =0.279, p=0.043) and deep-breathing heart rate variability (r s =−0.525, p<0.001). Intra-epidermal nerve fibre density (fibres/mm) compared with age-and sexmatched control subjects (11.06±0.82) was non-significantly reduced (7.37±0.93) in diabetic patients with a normal Neuropad response and significantly reduced in patients with a patchy (5.01±0.93) or absent (5.02±0.77) response (p= 0.02). The sensitivity of an abnormal Neuropad response in detecting clinical neuropathy (neuropathy disability score ≥5) was 85% (negative predictive value 71%) and the specificity was 45% (positive predictive value 69%). Conclusions/interpretation The Neuropad test may be a simple indicator for screening patients with diabetic neuropathy.

Useful Application of the Neuropad Test for Assessment of Diabetic Polyneuropathy

“…The present study applied this instrument to evaluate DPN and found that the mTCNS was significantly higher in patients with an abnormal and a patchy Neuropad response in comparison to those with a normal response. The time to complete the color change has been reported to be significantly associated with the clinical staging of DPN (8,16) diagnosed through NDS, showing that patients with time to change between 600 and 1,000 s, which may correspond to the patchy Neuropad responders in the current study, could have mild or moderate DPN diagnosed through the NDS. Likewise, patients with a time to color change between 1,000 and 1,200 s have moderate DNP and those scoring >1,200 s appear to have severe DNP.…”

“…Diabetic autonomic dysfunction has been principally evaluated centrally by assessing heart rate variability (4), and peripherally by assessing sweating using complex and expensive equipment (5). A new Neuropad test (6)(7)(8) for sudomotor function has been developed as a simple visual indicator test to evaluate DPN. On the other hand, several instruments (9,10) have developed for use in clinical practice because clinical evaluation of DPN is complex.…”

Corneal Confocal Microscopy – A Novel, Noninvasive Method to Assess Diabetic Peripheral Neuropathy

“…It was also shown that CCM correlate with the intraepidermal nerve fiber (IENF) loss in skin biopsies from the dorsum of the foot in diabetic patients [12] and may also show nerve repair after pancreas transplantation [24].…”

“…Only biopsy of the sural nerve and skin biopsy allows a direct examination of nerve fiber damage and repair [11]. However, both are invasive procedures, and assessment of therapeutic efficacy in clinical trials requires repeated biopsies [12].…”

“…It was also proven that CCM relates to intraepidermal nerve fiber loss and detects nerve fiber damage when the results of electrophysiology tests and quantitative sensory testing (QST) are normal [12].…”