Diode Laser as a Biomarker for Neuropathic Pain of Peripheral Origin.

The R61 will perform a four-part double-blind randomized crossover study transitioning from a pretreatment baseline phase, to randomized treatment with either lidocaine or an identical placebo patch, washout, and alternate arm. DLss measures will be obtained before and after each phase. Twice daily report of pain using a visual analogue scale will track severity of ongoing spontaneous pain in participants. The hybrid biomarker will distinguish between placebo and active treatment arms, will significantly correlate with extent of neuropathic pain reduction during lidocaine, but will not change during the placebo phase or no-treatment lead-in. If preset Go/No-Go criteria are met, the subsequent R33 validation will then compare lidocaine patch and placebo treatment in a blinded, randomized parallel arm study.