HLA-DRB1 and type 1 diabetes mellitus: As could be expected from many earlier studies, the heterozygous genotype DR3/DR4 at the DRB1 locus was associated with the lowest predictive probability of the T1D free survival to the age of 15, the estimate being 0.936 (0.926; 0.945 95% credible interval), compared to the average population T1D free survival probability of 0.995.