An illustration of different two-SNP interaction models. SNP 1 has genotype AA, Aa and aa; SNP 2 has genotype BB, Bb, and bb. A and B are the major alleles for SNP1 and 2, respectively.

Each entry in the tables represents the risk of the corresponding genotype combination relative to the baseline (AA/BB). (a) Multiplicative interaction model; (b) Unrestricted interaction model; (c) Average Risk Due to Interaction (ARDI) model.