The FBAT (family based association test) program was used to perform association tests in the family sample (Laird et al 2000). FBAT was developed on a principle similar to the transmission disequilibrium test (TDT), which controls for population stratification by comparing the alleles transmitted by parents to affected offspring with the nontransmitted alleles (Spielman et al 1993). The null hypothesis is “no linkage and no association” or “no association, in the presence of linkage”. The FBAT is a more general test that avoids confounding due to model misspecification as well as admixture or population stratification (http://www.biostat.harvard.edu/~fbat/default.html).
