title: A review on the design and reporting of studies on drug-gene interaction.
abstract: OBJECTIVE
  Methodological standards for clinical pharmacogenetic studies should be developed to improve reporting of studies and facilitate their inclusion in systematic reviews. The essence of these studies lies within the concept of effect modification.
  
  
  METHODS
  A narrative review discussing methodological issues in the design and reporting of pharmacogenetic studies.
  
  
  RESULTS
  Studying effect modification within a trial leads to the comparison of subgroups based on genotype. Differences in effect based on genotype should preferably be expressed in absolute terms (risk differences) to facilitate clinical decisions on treatment. Information on the distribution of potential effect modifiers or prognostic factors should be available to prevent a biased comparison of differences in effect between genotypes. The distribution of genotypes should also be presented and compared to Hardy-Weinberg equilibrium to check for selection bias. Additional points of interest include the possibility of selective nonavailability of biomaterial and the choice of a statistical model to study effect modification.
  
  
  CONCLUSIONS
  Additional methodological issues should be taken into account when designing and reporting pharmacogenetic studies, to ensure high study quality. We present several important issues for future studies investigating drug-gene interactions that can serve as a basis for further discussion on methodology in pharmacogenetics.
authors.affiliation: Department of Epidemiology, University of Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands. kim.smits@epid.unimaas.nl
authors.forename: Kim M
authors.initials: KM
authors.lastname: Smits
authors.forename: Jan S
authors.initials: JS
authors.lastname: Schouten
authors.forename: Luc J
authors.initials: LJ
authors.lastname: Smits
authors.forename: Foekje F
authors.initials: FF
authors.lastname: Stelma
authors.forename: Patty
authors.initials: P
authors.lastname: Nelemans
authors.forename: Martin H
authors.initials: MH
authors.lastname: Prins
mesh_terms: D005838:Genotype; D006801:Humans; D015233:Models, Statistical; D018579:Patient Selection; D010597:Pharmacogenetics / Q000592:standards*; D011379:Prognosis; D016032:Randomized Controlled Trials as Topic / Q000592:standards; D012107:Research Design / Q000592:standards*; D012306:Risk