title: Association between the TLR4 +896A>G (Asp299Gly) polymorphism and asthma: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To determine whether there is an association between the toll-like receptor 4 (TLR4) +896A>G single nucleotide polymorphism and asthma by conducting a systematic review and meta-analysis.
  
  
  METHODS
  The review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A systematic search for relevant studies was performed using PubMed (MEDLINE), Scopus, and HuGE Literature Finder databases with additional consultation of the reference lists of included studies. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated for the allelic comparison (G vs. A) and the genotypic comparison assuming a dominant genetic model (AG + GG vs. AA). I² statistics were calculated to assess the presence of between-study heterogeneity and funnel plots were inspected for indication of publication bias. Sensitivity analysis was performed to evaluate the influence of individual studies on the overall effect estimates.
  
  
  RESULTS
  Meta-analysis of nine studies consisting of 1838 asthma cases and 1764 controls did not find a significant association between TLR4 +896A>G and asthma (genotypic OR = 1.12, 95% CI: 0.91-1.39, p = .27). Between-study heterogeneity was not detected (I² = 0%) and publication bias was not evident. Sensitivity analysis demonstrated the stability of the null association.
  
  
  CONCLUSIONS
  The meta-analysis findings suggest a lack of direct association between the TLR4 +896A>G polymorphism and asthma, but gene-environment and gene-gene interaction effects and other considerations involving this polymorphism may exist. Therefore, further study is necessary to fully elucidate the role of TLR4 +896A>G in asthma.
authors.affiliation: University of Medicine and Health Sciences, New York, NY 10001, USA. schen@umhs-sk.net
authors.forename: Suzan
authors.initials: S
authors.lastname: Chen
mesh_terms: D000483:Alleles; D001249:Asthma / Q000235:genetics*; D059647:Gene-Environment Interaction; D005838:Genotype; D006801:Humans; D016017:Odds Ratio; D020641:Polymorphism, Single Nucleotide; D051197:Toll-Like Receptor 4 / Q000235:genetics*
chemical_list: C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4