Effects of transcutaneous electrical nerve stimulation (TENS) on proinflammatory cytokines: protocol for systematic review

BACKGROUND Pain reduction can be achieved by lowering proinflammatory cytokine levels in the blood. Transcutaneous electrical nerve stimulation (TENS) is a non-invasive physiotherapeutic resource for pain management, but evidence on the effectiveness of this device at reducing proinflammatory cytokines in the blood is unclear. This study systematically reviews the literature on the effect of TENS on proinflammatory cytokines. METHODS A systematic review protocol was developed based on searches of articles in six electronic databases and references of retrieved articles, contact with authors, and repositories of clinical trials. Eligibility criteria: publication in peer-reviewed journals, randomized clinical trials, use of TENS in the experimental group, and pre- and post-measurements of proinflammatory cytokines in the blood. Selection of the studies and extraction of the data will be carried out by two reviewers independently. Characteristics of the study, participants, interventions and outcomes were extracted and described. Assessments were performed on the risk of bias, level of evidence and the size of the intervention effect in the studies, according to GRADE guidelines and the Cochrane Handbook for Systematic Reviews. Clinical and statistical assessments compared the effects of the interventions (meta-analysis), taking into consideration any influencing characteristics of the studies (e.g., methods and application sites). DISCUSSION We anticipate that this review will strengthen evidence-based knowledge of the effect of TENS on proinflammatory cytokines and, as a result, direct new studies to benefit patients with specific pathologies. SYSTEMATIC REVIEW REGISTRATION PROSPERO, CRD42017060379 .