title: The association between Helicobacter pylori infection and inflammatory bowel disease based on meta-analysis.
abstract: BACKGROUND
  In humans there are epidemiological data suggesting a protective effect of Helicobacter pylori (H. pylori) infection against the development of autoimmune diseases and in addition, there are laboratory data illustrating H. pylori's ability to induce immune tolerance and limit inflammatory responses. Thus, numerous observational studies have examined the association between H. pylori infection and inflammatory bowel disease (IBD) with various results.
  
  
  OBJECTIVE
  We performed a meta-analysis of available studies to better define the association of H. pylori infection and IBD.
  
  
  METHODS
  Medical literature searches for human studies were performed through September 2014, using suitable keywords. In each study the risk ratio (RR) of H. pylori infection in IBD patients vs controls was calculated and pooled estimates were obtained using fixed- or random-effects models as appropriate. Heterogeneity between studies was evaluated using Cochran Q test and I(2) statistics, whereas the likelihood of publication bias was assessed by constructing funnel plots.
  
  
  RESULTS
  Thirty-three studies were eligible for meta-analysis, including 4400 IBD patients and 4763 controls. Overall 26.5% of IBD patients were positive for H. pylori infection, compared to 44.7% of individuals in the control group. There was significant heterogeneity in the included studies (Q = 137.2, df (Q) =32, I(2) ( )= 77%, p < 0.001) and therefore the random-effects model of meta-analysis was used. The obtained pool RR estimation was 0.62 (95% confidence interval (CI) 0.55-0.71, test for overall effect Z = -7.04, p < 0.001). There was no evidence of publication bias.
  
  
  CONCLUSIONS
  The results of this meta-analysis showed a significant negative association between H. pylori infection and IBD that supports a possible protective benefit of H. pylori infection against the development of IBD.
authors.affiliation: Gastroenterology Clinic, Henry Dunant Hospital Center, Athens, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Rokkas
authors.affiliation: Gastroenterology Unit, La Princesa University Hospital, Instituto de Investigación Sanitaria Princesa (IIS-IP), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Madrid, Spain.
authors.forename: J P
authors.initials: JP
authors.lastname: Gisbert
authors.affiliation: Department of Gastroenterology, Rabin Medical Center, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Niv
authors.affiliation: Department of Gastroenterology, Meath/Adelaide Hospital, Dublin, Ireland.
authors.forename: C
authors.initials: C
authors.lastname: O'Morain
keywords: Crohn’s disease; Helicobacter pylori; inflammatory bowel disease; meta-analysis; ulcerative colitis