Higher prevalence of autoantibodies to insulin and GAD65 in Swedish compared to Lithuanian children with type 1 diabetes

Abstract We compared the prevalence of beta-cell autoantibodies and genetic risk factors in Sweden and Lithuania. Ninety-six patients from Sweden and 96 from Lithuania matched for age and gender (1–15 years old, median age 9.0 years) were included. We analyzed autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA) and the protein tyrosine phosphatase like IA-2 (IA-2A) as well as risk-associated polymorphisms of HLA, insulin and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) genes. The frequency of patients positive for IAA and GADA was higher in Sweden than in Lithuania ( p  = 0.043 and 0.032). The differences remained even when the patients were matched for HLA, insulin and CTLA-4 risk genotypes. Patients with low levels of IAA had higher levels of HbA1c and ketones at diagnosis. The frequency of the risk haplotype DR4-DQ8 was higher in Swedish than in Lithuanian patients ( p  = 0.004), as well as the high-risk combination of DR4-DQ8 and DR3-DQ2 haplotypes ( p  = 0.009). Our results suggest that autoimmune process against insulin and GAD 65 is more common at diagnosis in children in areas with high incidence of type 1 diabetes (T1D), independent of genetic risk markers. Furthermore, the disease in patients with insulin autoantibodies seems to be clinically milder.