Third order linkage disequilibrium.

For third order linkage disequilibrium there is a constraint on the maximum value the disequilibrium can take, given pairwise disequilibria values and allele frequencies. As distinct from second order disequilibrium (considered in the context of a two locus model) there is also in some cases a constraint on the minimum value. The appropriate procedures to determine these maximum and minimum values are given, as well as numerical values utilizing HLA data.