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Family-based Association Test (FBAT)

  1. Nan M Laird

Published Online: 17 JAN 2011

DOI: 10.1002/9780470015902.a0022500



How to Cite

Laird, N. M. 2011. Family-based Association Test (FBAT). eLS. .

Author Information

  1. Harvard School of Public Health, Boston, Massachusetts, USA

Publication History

  1. Published Online: 17 JAN 2011


Statistical tests of association are commonly used to confirm or exclude a relationship between disease and selected genes. Tests which are based on data from unrelated individuals are very popular, but can be biased if the sample contains individuals with different genetic ancestries. Family-based Association tests avoid the problem of bias due to mixed ancestry by using within family comparisons. Many different family designs are possible, the most popular using parents and offspring, but others use just sibships. Dichotomous, measured and time-to-onset phenotypes can be accommodated. FBATs are generally less powerful than tests based on a sample of unrelated individuals, but special settings exist, for example testing for rare variants with affected offspring and their parents, where the family design has a power advantage.

Key Concepts:

  • Genetic tests based on population samples can be biased due to differing genetic ancestries.

  • Association designs using family members can avoid bias by using within family comparison.

  • The simplest family test is the TDT which uses affected offspring and their parents.

  • FBAT refers to a class of tests for family designs that can accommodate any type of genetic model, any phenotype and any family configuration, e.g. parents and their offspring, sibships or even general pedigrees.

  • In general, FBAT's are less powerful than their population-based counter-parts, and they generally also require more genotyping, but in some circumstances, e.g. for rare variants and in testing for gene–environment interactions, they can be more powerful.


  • genetic association test;
  • TDT;
  • family design;
  • trios;
  • discordant sibship test;
  • missing parents;
  • Mendel's laws;
  • linkage;
  • linkage disequilibrium