To assess the clinical utility of composite outcomes in studies examining outcomes of implantable neuromodulation therapies for pain: a systematic review.

BACKGROUND: Implantable neuromodulation therapies are offered to patients with certain refractory pain syndromes. These therapies are resource-intensive and effort-intensive and may be associated with significant adverse effects. Change in pain intensity score, an unidimensional measurement tool, is currently the most used eligibility criteria for patients to receive implanted neuromodulation devices. However, pain is a biopsychosocial phenomenon, and assessment of effectiveness of neuromodulation therapies using tools that incorporate multiple pain-related domains may be more relevant and accurate. Composite measures integrate multiple domains of patient well-being, enabling a clinically relevant assessment of treatment effects. This systematic review aims to evaluate the literature on the clinical utility and reliability of composite outcomes as a means to assess efficacy of implantable neuromodulation therapies for refractory pain. METHODS AND ANALYSIS: We will search Embase, MEDLINE, Cochrane Central Register of Controlled Trials and the WHO's International Clinical Trials Registry Platform. Searches will be limited to from inception of each database to 31 December 2025. Studies published in English will be considered eligible if they used composite outcomes to evaluate the efficacy and/or effectiveness of implantable neuromodulation therapies for treating refractory pain. The studies should investigate adult populations (aged ≥18 years) undergoing implantation for chronic refractory pain of moderate-to-severe intensity. Two reviewers will independently screen articles, extract data and review the risk of bias and the grade of evidence provided in the studies. Extracted data will include study details (author, year, country of origin), participant demographics (age, sex), sample sizes and intervention details. Outcome measures include pain intensity, physical health, mental health, quality of life, medication use and neuromodulation device explantation rates. Data will be collected at baseline, 3 months, 6 months and 12 months post-implantation where available. A meta-analysis will be formed if there is sufficient homogeneity in the studies and their data. ETHICS AND DISSEMINATION: As this study is a systematic review using data that has already been published in scientific literature or is publicly available, ethics approval is not required. For dissemination, we plan to share the findings of our review through multiple academic and clinical channels. The completed review will be submitted for publication in a peer-reviewed journal relevant to pain medicine or neuromodulation. PROSPERO REGISTRATION NUMBER: CRD42025631488.