Supplementary Material for: Association between Toll-Like Receptor 4 T399I Gene Polymorphism and the Susceptibility to Crohn’s Disease: A Meta-Analysis of Case-Control Studies

Background/Aims: This article was undertaken to investigate the association of toll-like receptor 4 (TLR4) polymorphism (Thr399Ile) and risk of Crohn’s disease (CD) by performing a meta-analysis. Methods: Articles were chosen based on PubMed, Embase, China National Knowledge Internet, and Chinese Wanfang databases (up to 12th October 2016). Specific inclusion criteria were used to evaluate articles. Meta-analysis was performed by using a random or fixed effect model. Fifteen eligible case-control studies were finally included into this meta-analysis. We estimated the summary OR with its corresponding 95% CI to assess the association. Results: Summary results of this meta-analysis showed a moderate association between the TLR4 T399I polymorphism and the risk of CD (allele model: OR 1.26, 95% CI 1.06–1.50, p = 0.009; heterozygote model: OR 1.36, 95% CI 1.11–1.66, p = 0.003; dominant model: OR 1.35, 95% CI 1.10–1.64, p = 0.004; homozygote model: OR 1.08, 95% CI 0.44–2.64, p = 0.866; recessive model: OR 0.97, 95% CI 0.40–2.35, p = 0.946). Stratified analysis on geographical area, ethnicity, and genotypic methods suggested that the polymorphism was associated with increased risk of CD in Asia and Asians, and “T” allele only moderately increased CD risk within polymerase chain reaction-restricted fragment length polymorphism. Conclusions: Our meta-analysis suggests that TLR4 T399I polymorphism is moderately associated with susceptibility to CD, and more studies are needed to confirm our conclusion.