Effect of metformin use on graft and patient survival in kidney transplant recipients with type 2 diabetes: a systematic review protocol

Introduction Metformin is a first-line antihyperglycaemic agent for type 2 diabetes (T2DM). In addition to glycaemic control, it offers benefits related to cardiovascular health, weight neutrality and metabolic syndrome. However, its benefits in kidney transplant recipients remain unclear as metformin use is controversial in this population due to a lack of evidence and there are recommendations against its use in patients with poor kidney function. Hence, we seek to describe a protocol for a systematic review, which will assess the impact of metformin use on graft survival and mortality in kidney transplant recipients.Methods This protocol was guided by the standards of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Protocols 2015. We will search empirical databases such as MEDLINE, Embase, Cochrane Library, CINAHL and Web of Science Core Collection for relevant studies conducted in kidney transplant recipients using metformin, which report outcomes related to graft and patient survival. All studies meeting these criteria in adults and published in English from inception to 2023 will be included in our review. We will employ the Cochrane Risk of Bias Tool 2 for randomised controlled trials and the Risk of Bias in Non-randomised Studies of Intervention for non-randomised studies. We will present our data and study characteristics in a table format and determine if a meta-analysis can be performed by clinical and methodological heterogeneity, using the I2 statistics. If a meta-analysis cannot be performed, we will provide a narrative synthesis of included studies using the Synthesis Without Meta-Analysis Reporting Guideline.Ethics and dissemination Ethical approval will not be required for this review as the data used will be extracted from already published studies with publicly accessible data. As this study will assess the impact of metformin use on graft and patient survival in kidney transplant recipients, evidence gathered through it will be disseminated using traditional approaches that include open-access peer-reviewed publication, scientific presentations and a report. We will also disseminate our findings to appropriate academic bodies in charge of publishing guidelines related to T2DM and transplantation, as well as patient and research centred groups.PROSPERO registration number CRD42023421799.