Tests for association - 3: Using siblings to provide control alleles
For some diseases it may be difficult to obtain parents for a TDT
sample. It may sometimes be possible to deduce parental alleles from the
siblings of cases and then perform the TDT, but subtle biases can arise with this procedure and
much potentially useful information may be lost.
A number of methods have been proposed which use siblings, rather than
parents, to provide control alleles: