Is there a link between seropositivity to Helicobacter pylori and hepatitis A virus? A systematic review

Background: Since hepatitis A virus (HAV) is acquired primarily through the fecal-oral pathway, several investigators have used HAV seropositivity as a proxy for exposure to this pathway. This paper is a critical review of the evidence relevant to the association between seropositivity to HAV and Helicobacter pylori, and considers the validity of comparisons for testing the hypothesis that H. pylori spreads by the fecal-oral route. Materials and methods: : A Medline search identified reports of all types published in the English language literature that were linked to the keywords 'Campylobacter pylori', 'hepatitis A', or 'Helicobacter pylori', cross-referenced with 'seroepidemiology', 'seroprevalence', or 'seropositivity'. Studies identified by the search were included in the review if they used specific IgG antibodies to classify the serostatus of subjects for both HAV and H. pylori infection and provided an estimate of the magnitude of the association between HAV and H. pylori or information that permitted calculation of an odds ratio (OR). Results: Out of the 21 studies identified, 15 met the inclusion criteria. The studies showed ORs for an association of HAV and H. pylori that ranged from 0.81 to 8.4. After adjustment for potential confounders, ORs shifted toward the null. They also showed that HAV seroprevalence is lower than H. pylori seroprevalence in early life and then becomes higher in later life. Thus in most populations, the trends cross over at some point. Conclusion: The observed associations between the two infections are generally overestimated by the confounding effects of age and socio-economic status-related factors, and when these factors are controlled, the association becomes weak. Moreover, HAV infection elicits a long-term antibody response, while H. pylori infection does not. Consequently, serostatus comparison does not constitute a convincing test of the fecal-oral transmission hypothesis for H. pylori. (C) 2009 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.