Aims/hypothesis: The study aimed to assess, in multiple populations, the role of HLA alleles on early and late age at onset of type 1 diabetes.
Methods: Stepwise linear regression models were used to determine which HLA class I and class II risk alleles to include. High-resolution genotyping data for patients from the Type 1 Diabetes Genetics Consortium (T1DGC) collection (n = 2,278) and four independent cohorts from Denmark, Sardinia and the USA (Human Biological Data Interchange [HBDI] and Joslin Diabetes Center) (n = 1,324) (total n = 3,602) were used to assess the role of HLA variation on age of onset and predict early onset (age ≤ 5 years) and late onset (age ≥ 15 years) of type 1 diabetes.
Results: In addition to carriage of HLA class I alleles A*24:02, B*39:06, B*44:03 and B*18:01, HLA class II DRB1-DQB1 loci significantly contributed to age at onset, explaining 3.4% of its variance in the combined data. HLA genotypes, together with sex, were able to predict late onset in all cohorts studied, with AUC values ranging from 0.58 to 0.63. Similar AUC values (0.59-0.70) were obtained for early onset for most cohorts, except in the Sardinian study, in which none of the models tested had significant predictive power.
Conclusions/interpretation: HLA associations with age of onset are consistent across most white populations and HLA information can predict some of the risk of early and late onset of type 1 diabetes. Considerable heterogeneity was observed between Sardinian and other populations, particularly with regard to early age of onset.