Helicobacter pylori and gastrointestinal and neurological diseases Study protocol of an umbrella review of systematic reviews and meta-analyses

Background: Systematic reviews showed that Helicobacter pylori (HP) infection is a major risk for developing gastric cancer and gastric ulcer and that it might be the cause of inflammatory bowel diseases, functional gastrointestinal disorders, and neurological diseases like Alzheimer disease. However, the robustness of the evidence was not tested. We will perform an umbrella review to systematically evaluate current evidence on the correlation between HP infection and gastrointestinal and neurological diseases. Methods: We will search OVID MEDLINE, EMBASE, and the Cochrane library for systematic reviews that evaluate the correlation of HP with gastrointestinal and neurological diseases, from inception to 1 July, 2019. Two reviewers will independently screen titles and abstracts of retrieved articles for eligible studies, and they will extract information for data analysis. We will assess heterogeneity between studies using I-2 statistics and evaluate small-study effect in each systematic review through Egger test. Excess significance bias will be evaluated by compared the expected number of clinical studies with positive findings with the observed number. Quality of each systematic review will be assessed by using AMSTAR2 checklist.