Our Wisconsin Family T1D Study involving non-related random healthy controls, recent-onset (RO) T1D, healthy autoantibody-positive (Ab+) siblings of T1D probands and longstanding (LS) T1D subjects, has allowed us to develop an HLA DQA1/B1 haplotype risk assessment tool that recognizes susceptible (S), resistant (R), weakly protective (Y) and neutral haplotypes (X). Here, HLA-DQA1 is linked to type 1 diabetes mellitus.