HLA DR/DQ alleles and risk of type I diabetes in childhood: a population–based case–control study

The objective was to evaluate HLA DR/DQ alleles and their risk factor for type 1 diabetes in the Abruzzo region (central Italy). Sixty incident cases from the Abruzzo region were studied together with 120 unrelated control subjects living in the same administrative areas. The relative risk of diabetes associated with the alleles under study was calculated by deriving the odds ratio (OR) maximum likelihood estimates and their 95% confidence intervals (CI) by the exponentiation of the logistic regression beta–parameter. The combination DRB1*03/DQA1*0501/DQB1*0201 was found in 20.0% of patients and 7.1% of the control subjects, conferring an OR of 4.04 and a CI of 1.97–8.49. The combination DRB1*04/DQA1*0301/DQB1*0302 was found in 23.3% of diabetic patients and 6.7% of controls, giving an OR of 5.69 and a CI of 2.77–12.05. DRB1*11/DQA1*0505/DQB1*0301 and DQA1*0505/DQB1*0301 were negatively associated with type 1 diabetes (OR=0.27, CI 0.11–0.57; OR=0.07, CI 0.02–0.19). The DQA1 genotype at risk was found to be DQA1*0301/DQA1*0501: OR=23.80, CI 2.97–190.89, as it occurred with the highest frequency in the patient group. The DQB1 genotype at risk was found to be DQB1*0201/DQB1*0302, which occurred in 13.3% of patients but in only 1.1% of the control group (OR=29.75, CI 5.36–549.25). Our results shed further light on the risk of development of this disease during a specific time period in an area where the overall incidence of type 1 diabetes is known.