A Test for Peripheral Neuropathy?

Peripheral neuropathy is a distressing complaint that is usually encountered as a complication of diabetes. There is a loss of sensation, or numbness, in the feet and hands, accompanied by pain, which is usually felt as a tingling or burning. As the name implies, it’s due to damage to the sensory nerves supplying one or more limbs. About half of all diabetics will eventually develop peripheral neuropathy. If diabetes is not the cause, it’s often difficult to determine exactly what the real cause is.

Greek researchers have now developed a simple way to detect peripheral neuropathy, and published their findings in Diabetes Care. The test consists of a pad called the Indicator Plaster Neuropad (IPN), which, after 10 minutes’ application, turns pink when nerve conduction is normal and blue when peripheral neuropathy is present. The basis of the color change is a defect in the sudomotor, or sweat-controlling nerves under the pad.

In a study on 156 diabetics, the examining doctor determined that 57% of them had peripheral neuropathy. The IPN test had very good sensitivity – 87% - but the specificity was lower – 66%; this means the test was good at excluding people from a wrong diagnosis of neuropathy, but less good at capturing all patients with the condition. Overall agreement between the doctor and the test reading was very high, at 90%. The authors of the study warn that older patients with vision problems may have some difficulty in evaluating the test in a self-testing mode.

This test is much, much simpler and cheaper than the previous ‘gold-standard’ for diagnosing peripheral neuropathy – nerve conduction velocity studies. Self-administration is also feasible except for the very old and the visually impaired. It looks like it will prove to be a useful addition to the care of diabetics.