title: Genetic heterogeneity of self-reported ancestry groups in an admixed Brazilian population.
abstract: BACKGROUND
  Population stratification is the main source of spurious results and poor reproducibility in genetic association findings. Population heterogeneity can be controlled for by grouping individuals in ethnic clusters; however, in admixed populations, there is evidence that such proxies do not provide efficient stratification control. The aim of this study was to evaluate the relation of self-reported with genetic ancestry and the statistical risk of grouping an admixed sample based on self-reported ancestry.
  
  
  METHODS
  A questionnaire that included an item on self-reported ancestry was completed by 189 female volunteers from an admixed Brazilian population. Individual genetic ancestry was then determined by genotyping ancestry informative markers.
  
  
  RESULTS
  Self-reported ancestry was classified as white, intermediate, and black. The mean difference among self-reported groups was significant for European and African, but not Amerindian, genetic ancestry. Pairwise fixation index analysis revealed a significant difference among groups. However, the increase in the chance of type 1 error was estimated to be 14%.
  
  
  CONCLUSIONS
  Self-reporting of ancestry was not an appropriate methodology to cluster groups in a Brazilian population, due to high variance at the individual level. Ancestry informative markers are more useful for quantitative measurement of biological ancestry.
authors.affiliation: Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, DF, Brazil.
authors.forename: Tulio C
authors.initials: TC
authors.lastname: Lins
authors.forename: Rodrigo G
authors.initials: RG
authors.lastname: Vieira
authors.forename: Breno S
authors.initials: BS
authors.lastname: Abreu
authors.forename: Paulo
authors.initials: P
authors.lastname: Gentil
authors.forename: Ricardo
authors.initials: R
authors.lastname: Moreno-Lima
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Oliveira
authors.forename: Rinaldo W
authors.initials: RW
authors.lastname: Pereira
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D044383:Black People; D001938:Brazil; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D018740:Genetic Heterogeneity; D030661:Genetic Privacy; D005828:Genetics, Population; D006801:Humans; D007199:Indians, South American / Q000706:statistics & numerical data*; D057566:Self Report; D012647:Self-Assessment; D011795:Surveys and Questionnaires; D044465:White People