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Editorial: the prevalence of Helicobacter pylori infection worldwide—knowns and unknowns. Authors' reply

all included countries, there was also considerable heterogeneity. The prevailing explanation is that this variability reflects real differences in the prevalence of the infection. However, as Zamani et al noted, our confidence in these results is undermined because of the variability in the sampling methods and diagnostic tests among studies. Furthermore, all the comparative analyses reported in this paper (between countries and continents; male/female; children/adults; older/recent studies) were between-study comparisons, which, understandably, are less reliable than within-study comparisons, which have not been conducted. Ideally, the risk of bias (methodological “quality”) of individual studies should have been assessed with a valid tool or a justified modification thereof, and subgroup analyses should have been performed for the (few) studies at low risk of bias vs studies at not-low risk of bias. When the certainty (“quality”) of the evidence is assessed by GRADE (Grading of Recommendations Assessment, Development and Evaluation), it is “very low,” meaning that further research is very likely to change existing estimates. Does this mean that we need yet another SRMA that addresses the above-mentioned issues? We do not think so. It is unlikely that such a project would produce much incremental knowledge. The overall conclusions would remain unchanged: large variability in the prevalence of H. pylori infection and very low certainty in the estimates. What is needed is further and better primary research with representative sampling, accurate diagnostic methods and high reporting standards that will provide accurate estimates of the prevalence of H. pylori infection in separate countries, including their regions and subpopulations. The evidence for eradicating H. pylori in the general population as a preventive strategy for gastric cancer is accumulating. However, the decision to implement such strategies will be taken by distinct national or regional governments only if accurate and reliable prevalence maps are available for their own jurisdiction. Ideally, such research efforts should also map the prevalence of H. pylori antibiotic resistance; such data are vital for the appropriate selection of eradication therapy, but currently are largely absent for most regions and countries.