Joint effect and interaction between polymorphisms and H. pylori infection on risk of intestinal metaplasia and dysplasia*.

*This analysis was restricted to 2078 participants who had diagnosis for H. pylori infection.†Odds ratios (ORs) and 95% confidence intervals (CI) for the risk of intestinal metaplasia and dysplasia were estimated in reference to superficial gastritis/chronic atrophic gastritis, and adjusted for age, gender, smoking and drinking status. Participants with missing data on any of variables were excluded from the analysis.‡P for trend was calculated by assigning an ordinal value (1–6) to each combination of genotype and H. pylori infection (1 = homozygote wild without H. pylori infection, 2 = heterozygote without H. pylori infection, 3 = homozygote variant without H. pylori infection, 4 = homozygote wild with H. pylori infection, 5 = heterozygote with H. pylori infection, 6 = homozygote variant with H. pylori infection) and adding it as a continuous variable to the multivariate model.§Likelihood ratio test was used to calculate the P value for interaction by comparing the two models with and without the product term of genotypes and H. pylori infection.