Altered pain processing in people with type I and II diabetes: a protocol for a systematic review and meta-analysis of pain threshold and pain modulation mechanisms

BACKGROUND: Peripheral neuropathies are a common complication in patients with diabetes. Changes in nerve function and central pain processing can be quantified by assessing pain thresholds and pain modulation mechanisms. AIM: To summarise the literature which compares pain thresholds and pain modulation mechanisms in people with diabetes without neuropathies, with non-painful diabetic neuropathies and with painful diabetic neuropathies, and in people without diabetes. METHODS: A systematic review and meta-analysis will be conducted. Terms related to diabetes, pain thresholds and pain modulation mechanisms will be combined in a structured search in MEDLINE, CINAHL, EMBASE, the Cochrane Library, SPORTDiscus, Web of Science and PEDro. Publications on adults (18 years and older) with diabetes and at least one pain threshold measure following thermal, mechanical or electrical stimuli and/or at least one pain modulation mechanisms (temporal summation or conditioned pain modulation) with a comparison group will be considered. There will be no restriction regarding language or year of publication. One investigator will screen records based on title and abstract (ESS). Two independent investigators (ESS and MC) will select full-text papers and assess risk of bias using a modified Downs and Black checklist. Potential disagreements will be resolved with a third investigator (LB). One investigator (ESS) will extract all data and a second investigator (MS) will extract data for 20% of the papers to verify accuracy of the process. A sensitivity analysis for publication bias will be conducted. DISCUSSION: This systematic review and meta-analysis will summarise the evidence on pain threshold profiles and pain modulation mechanisms in people with diabetes without and with neuropathies (both painful and non-painful). This will provide more insight in the clinical presentation and progression of diabetic neuropathies. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42018088173 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13643-018-0895-2) contains supplementary material, which is available to authorized users.