title: Translational medicine and reliability of single-nucleotide polymorphism studies: can we believe in SNP reports or not?
abstract: BACKGROUND
  The number of genetic association studies is increasing exponentially. Nonetheless, genetic association reports are prone to potential biases which may influence the reported outcome.
  
  
  OBJECTIVE
  We hypothesized that positive outcome for a determined polymorphism might be over-reported across genetic association studies analysing a small number of polymorphisms, when compared to studies analysing the same polymorphism together with a high number of other polymorphisms.
  
  
  METHODS
  We systematically reviewed published reports on the association of glutathione s-transferase (GST) single-nucleotide polymorphisms (SNPs) and cancer outcome.
  
  
  RESULTS
  We identified 79 eligible trials. Most of the studies examined the GSTM1, theGSTP1 Ile105Val mutation, and GSTT1polymorphisms (n = 54, 57 and 46, respectively). Studies analysing one to three polymorphisms (n = 39) were significantly more likely to present positive outcomes, compared to studies examining more than 3 polymorphisms (n=40) p = 0.004; this was particularly evident for studies analysing the GSTM1polymorphism (p =0.001). We found no significant associations between journal impact factor, number of citations, and probability of publishing positive studies or studies with 1-3 polymorphisms examined.
  
  
  CONCLUSIONS
  We propose a new subtype of publication bias in genetic association studies. Positive results for genetic association studies analysing a small number of polymorphisms (n = 1-3) should be evaluated extremely cautiously, because a very large number of such studies are inconclusive and statistically under-powered. Indeed, publication of misleading reports may affect harmfully medical decision-making and use of resources, both in clinical and pharmacological development setting.
authors: Onkologkliniken Sörmland, Mälarsjukhuset, Eskilstuna, Sweden.
authors: Antonis
authors: A
authors: Valachis
authors: Davide
authors: D
authors: Mauri
authors: Christodoulos
authors: C
authors: Neophytou
authors: Nikolaos P
authors: NP
authors: Polyzos
authors: Lampriani
authors: L
authors: Tsali
authors: Antonios
authors: A
authors: Garras
authors: Evangelos G
authors: EG
authors: Papanikolau
mesh_terms: D000483:Alleles; D016206:Databases, Bibliographic / Q000706:statistics & numerical data; D003657:Decision Making; D056726:Genetic Association Studies; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D055811:Journal Impact Factor; D009363:Neoplasm Proteins / Q000235:genetics; D009369:Neoplasms / Q000201:enzymology / Q000235:genetics / Q000401:mortality; D020641:Polymorphism, Single Nucleotide; D039781:PubMed / Q000706:statistics & numerical data; D017594:Publication Bias; D015203:Reproducibility of Results; D057170:Translational Research, Biomedical; D016896:Treatment Outcome
chemical_list: D009363:Neoplasm Proteins; D005982:Glutathione Transferase