Importantly, the overall HLA allele frequencies were in line with those assumed, but there were certain batches with biased frequencies suggesting that those may include high numbers of a specific patient group; the increased frequencies of HLA-DRB1*04:01, HLA-DQA1*03:01 and HLA-DQB1*03:02 alleles in a few batches are most likely due to a high number of T1D patients in these batches. This evidence concerns the gene HLA-DRB1 and type 1 diabetes mellitus.