Table 4. Joint effect and interaction between polymorphisms and H. pylori infection on risk of intestinal metaplasia and dysplasia^*.

Variant	Genotype	H. pylori infection	OR (95% CI)†	P for trend‡
rs2910164	GG	Negative	1.00 (referent)
	GC	Negative	1.01 (0.68–1.50)
	CC	Negative	1.08 (0.48–2.41)
	GG	Positive	2.44 (1.80–3.31)
	GC	Positive	2.55 (1.86–3.49)
	CC	Positive	2.25 (1.43–3.54)	<0.001
	P for interaction§		0.35
rs895819	TT	Negative	1.00 (referent)
	TC	Negative	0.87 (0.51–1.48)
	CC	Negative	0.93 (0.52–1.66)
	TT	Positive	1.83 (1.09–3.10)
	TC	Positive	2.09 (1.28–3.39)
	CC	Positive	2.77 (1.68–4.56)	<0.001
	P for interaction§		0.92

^*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.