title: Do polymorphisms of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene affect the risk of childhood acute lymphoblastic leukemia?
abstract: Meta-analysis has become an important statistical tool in genetic association studies, since it may provide more powerful and precise estimates. However, meta-analytic studies are prone to several potential biases not only because the preferential publication of "positive'' studies but also due to difficulties in obtaining all relevant information during the study selection process. In this letter, we point out major problems in meta-analysis that may lead to biased conclusions, illustrating an empirical example of two recent meta-analyses on the relation between MTHFR polymorphisms and risk of acute lymphoblastic leukemia that, despite the similarity in statistical methods and period of study selection, provided partially conflicting results.
authors.forename: Tiago Veiga
authors.initials: TV
authors.lastname: Pereira
authors.forename: Martina
authors.initials: M
authors.lastname: Rudnicki
authors.forename: Alexandre Costa
authors.initials: AC
authors.lastname: Pereira
authors.forename: Maria S
authors.initials: MS
authors.lastname: Pombo-de-Oliveira
authors.forename: Rendrik França
authors.initials: RF
authors.lastname: Franco
mesh_terms: D015982:Bias; D020022:Genetic Predisposition to Disease; D006801:Humans; D015201:Meta-Analysis as Topic; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D011110:Polymorphism, Genetic; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics*
chemical_list: D042965:Methylenetetrahydrofolate Reductase (NADPH2)