A randomised, patient-assessor blinded, sham-controlled trial of external non-invasive peripheral nerve stimulation for chronic neuropathic pain following peripheral nerve injury (EN-PENS trial): study protocol for a randomised controlled trial

Abstract

BackgroundEight percent of people in the UK are estimated to have persistent (chronic) neuropathic pain, and for many there is no effective treatment. Medications are the most common first-line treatment but often have limited benefit or adverse events. Surgical treatments, such as spinal cord stimulation, are then often considered. External non-invasive peripheral nerve stimulation (EN-PENS) is a form of electrical stimulation that involves placing a pen-shaped electrode onto the skin, which can be easily self-administered by patients. Observational studies suggest that EN-PENS may relieve pain for people with localised neuropathic pain; however, there is currently no evidence from controlled trials to confirm the efficacy and confidently determine the effect size for patients with longstanding neuropathic pain.MethodsEN-PENS is a single-site, blinded, randomised controlled parallel-group superiority add-on trial with a 1:1 allocation ratio, designed to evaluate the efficacy of treatment versus control treatment in 76 patients with longstanding neuropathic pain following peripheral nerve injury. Patients with moderate to -severe neuropathic pain following peripheral nerve injury will be randomised to receive either the active or control treatment, followed by an optional treatment extension or treatment switch to the alternative treatment arm. The primary outcome is average 24-h pain intensity recorded on an 11-point (0–10) numerical rating scale, averaged over the last 7 days of treatment.DiscussionStudy results will be used to inform potential treatment efficacy and cost-effectiveness of EN-PENS for this population group.Trial registration ISRCTN53432663. Registered on 7 July 2016.

Mechanistically informed non-invasive peripheral nerve stimulation for peripheral neuropathic pain: a randomised double-blind sham-controlled trial

“…The study was registered on the ISRCTN registry, registry number: ISRCTN53432663. The full protocol was published before initiation of the trial [ 17 ]. The trial was conducted in accordance with the original protocol.…”

“…A correlation of 0∙5 between the baseline and outcome pain scores was assumed (0.64 in observational study data). Therefore, based on a 5% significance level, 90% power, and assumed 30% attrition rate, it was calculated that 38 participants per group were required to show a difference of 1.5 units in the primary outcome between groups, further details are provided within the published protocol [ 17 ].…”

Mechanistically Informed Non-Invasive Peripheral Nerve Stimulation for Peripheral Neuropathic Pain: A Randomised Double-Blind Sham-Controlled Trial

“…The full protocol was published before initiation of the trial. 17 The trial was conducted in accordance with the original protocol. Data collected ended when all patients had completed the optional treatment extension/swap and was predetermined before commencement of the trial.…”

“…Therefore, based on a 5% signi cance level, 90% power, and assumed 30% attrition rate, it was calculated that 38 participants per group were required to show a difference of 1•5 units in the primary outcome between groups, further details are provided within the published protocol. 17…”

“…Details of the healthcare resource use and cost analysis are described in the published protocol. 17 A preplanned health economic analysis to estimate NHS perspective cost-effectiveness, will be reported separately.…”