title: Lack of association of apolipoprotein E (Apo E) ε2/ε3/ε4 polymorphisms with primary open-angle glaucoma: a meta-analysis from 1916 cases and 1756 controls.
abstract: BACKGROUND
  A number of case-control studies were conducted to investigate the association of apolipoprotein E (Apo E) polymorphisms with primary open angle glaucoma (POAG). But the results remain controversial. This meta-analysis aims to comprehensively evaluate the relationship between a common ε2/ε3/ε4 polymorphism in Apo E gene on the risk of POAG.
  
  
  METHODS
  A comprehensive literature search for studies published up to April 2013 was performed. Summary odds ratios (ORs) and 95% confidence intervals (CI) were calculated employing random-effects models irrespective of between-study heterogeneity. Publication bias of literatures was evaluated using funnel plots and Egger's test.
  
  
  RESULTS
  A total of 12 studies including 1916 cases and 1756 controls meeting the predefined criteria were involved in this meta-analysis. Overall, the Apo E ε2 allele and ε4 allele were not associated with POAG, compared with those carrying ε3 allele, with ORs of 0.98 (95% CI, 0.79 to 1.23; P=0.872) and 1.05 (95% CI, 0.78 to 1.41; P=0.743), respectively. Genotypic analysis also found no significant association between the ε4 carriers (ε3/ε4+ε4/ε4), ε2 carriers (ε2/ε3+ε2/ε2) and POAG, compared with participants with Apo E ε3/3, with ORs of 0.91 (95% CI, 0.66 to 1.25; P=0.543) and 1.08 (95% CI, 0.74 to 1.57; P=0.694), respectively. In the subgroup analysis by ethnicity, source of controls, genotyping methods, Hardy-Weinberg equilibrium or not, or type of the POAG, still no obvious associations were found.
  
  
  CONCLUSIONS
  This meta-analysis suggests that Apo E ε2/ε3/ε4 polymorphisms may not be associated with the risk of POAG. However, well-designed studies with larger sample size and more ethnic groups are required to further validate the results.
authors.affiliation: Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-Sen University, Guangzhou, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Minwen
authors.initials: M
authors.lastname: Zhou
authors.forename: Wenbin
authors.initials: W
authors.lastname: Huang
authors.forename: Shida
authors.initials: S
authors.lastname: Chen
authors.forename: Xiulan
authors.initials: X
authors.lastname: Zhang
mesh_terms: D053329:Apolipoprotein E2 / Q000235:genetics*; D053318:Apolipoprotein E3 / Q000235:genetics*; D053327:Apolipoprotein E4 / Q000235:genetics*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000235:genetics*; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics*
chemical_list: D053329:Apolipoprotein E2; D053318:Apolipoprotein E3; D053327:Apolipoprotein E4
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