Meta analysis and an application in genetic studies

Aim: Meta-analysis is a collection of methods that enable the combination of findings from independent studies for specific subject with appropriate statistical methods in this study. Meta-analytic methods will be introduced and an illustration will be performed on a genetic data. Schizophrenia is a psychiatric disorder affecting 1% of the world population and involves many genetic and environmental factors. The catechol-O-methyltransferase (COMT) is known to be a schizophrenia-sensitive the COMT gene. For the illustration, the odds ratios obtained based on the allele frequency for the rs737865 SNP of the COMT gene (single nucleotide polymorphism) and schizophrenia will be combined. Material and Method: For keywords "COMT (rs737865) schizophrenia" the publications were searched in the Pubmed, Web of Science and Google Scholar databases until December 2016. 15 studies that met our inclusion criteria and 4 studies that provided gender-specific data were used with appropriate meta analytic methods for common estimation of odds ratios based on allele frequencies via STATA 14.0. Results: We used the Dersimonian Laird method under random effect model for estimation of the common odds ratio=1,066 (95% C.I.=0,985-1,153) for 15 studies. For 4 studies fixed effect models were used for men and women separately. For men and women the results found to be OR= 1.138 (95% CI = 0.975-1.328), OR = 1.138 (95% CI = 0.975-1.328) respectively. Conclusion: A proper meta-analytical method has yielded a common risk estimate and it is found to be that having a C or T allel for the COMT gene rs737865 SNP does not cause a risk for schizophrenia for total data or men. But for women, it is found to be that having a T allel increases the risk of schizophrenia.