Measurement of small fibre pain threshold values for the early detection of diabetic polyneuropathy

To investigate whether Aδ and C fibre pain threshold values, measured using intra-epidermal electrical stimulation (IES), in people with and without Type 2 diabetes are useful in evaluating diabetic polyneuropathy (DPN) severity.

Aδ and C fibre pain threshold values were measured in Japanese people with (n = 120) and without (n = 76) Type 2 diabetes by IES. Nerve conduction studies and other tests were performed to evaluate diabetic complications.

Aδ and C fibre pain threshold values were high in people with diabetes compared with control subjects (Aδ fibre: 0.050 vs. 0.030 mA, P < 0.01; C fibre: 0.180 vs. 0.070 mA, P < 0.01). Participants with diabetes and neuropathy had significantly higher Aδ and C fibre pain threshold values than participants without neuropathy (Aδ fibres 0.063 vs. 0.039 mA, P < 0.01; C fibres 0.202 vs. 0.098 mA, P < 0.05). C fibre pain threshold values were significantly higher in participants with diabetes and diabetic microvascular complications than in participants without complications. Threshold values increased with complication progression. When DPN was diagnosed according to the Diabetic Neuropathy Study Group in Japan criteria, the cut-off for the C fibre pain threshold values was 0.125 mA (area under the curve 0.758, sensitivity 81.5%, specificity 61.5%). The IES test took less time (P < 0.01) and was less invasive (P < 0.01) than the nerve conduction studies.

Intra-epidermal electrical stimulation is a non-invasive and easy measurement of small fibre pain threshold values. It may be clinically useful for C fibre measurement to diagnose early DPN as defined by the Diabetic Neuropathy Study Group in Japan criteria.