title: Interleukin-18 promoter polymorphisms and plasma levels are associated with increased risk of periodontitis: a meta-analysis.
abstract: OBJECTIVE
  Emerging evidence has showed that interleukin-18 (IL-8) promoter polymorphisms and plasma IL-18 levels may be associated with increased risk of periodontitis, but individually published results are inconclusive. The aim of this meta-analysis was to derive a more precise estimation of these associations.
  
  
  METHODS
  A literature search of PubMed, Cochrane Library, Embase, Web of Science, SpringerLink, China BioMedicine and China National Knowledge Infrastructure databases was conducted on articles published before April 1st, 2013. Crude odds ratio (OR) or standardized mean difference (SMD) with 95 % confidence intervals (CI) were calculated.
  
  
  RESULTS
  Nine case-control studies were included with a total of 576 periodontitis patients and 458 healthy controls. Two common polymorphisms (-607A > C and -137G>C) in the IL-18 gene were addressed. Our meta-analysis results indicated that the C variant of IL-18 -607A>C polymorphism was associated with increased periodontitis risk (C allele vs. A allele: OR = 1.86, 95 % CI: 1.30-2.65, P = 0.001; AC+CC vs. AA: OR = 2.64, 95 % CI: 1.34-5.21, P = 0.005). There was also a significant association between the C variant of IL-18 -137G>C polymorphism and an increased periodontitis risk (C allele vs. G allele: OR = 1.47, 95 % CI: 1.13-1.91, P = 0.004; GC+CC vs. GG: OR = 1.66, 95 % CI: 1.21-2.29, P = 0.002). Furthermore, the mean levels of plasma IL-18 of periodontitis patients were also higher than those of healthy controls (SMD = 1.18, 95 % CI: 0.51-1.85, P = 0.001).
  
  
  CONCLUSIONS
  The current meta-analysis suggests that IL-18 promoter polymorphisms and plasma IL-18 levels are associated with increased risk of periodontitis. IL-18 promoter polymorphisms and elevated plasma IL-18 levels may be useful biomarkers for predicting the development of periodontitis.
authors.affiliation: Department of Prosthodontics, The Second Affiliated Hospital of Liaoning Medical University, Shanghai Road No.49, Jinzhou, 121000, People's Republic of China, ll2h_lzg@126.com.
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Li
authors.forename: Jin-Juan
authors.initials: JJ
authors.lastname: Li
authors.forename: Chang-An
authors.initials: CA
authors.lastname: Sun
authors.forename: Yuan
authors.initials: Y
authors.lastname: Jin
authors.forename: Wei-Wei
authors.initials: WW
authors.lastname: Wu
mesh_terms: D016022:Case-Control Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D020382:Interleukin-18 / Q000097:blood / Q000235:genetics*; D010518:Periodontitis / Q000097:blood / Q000453:epidemiology / Q000235:genetics*; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012306:Risk
chemical_list: D020382:Interleukin-18