The BDD study is a nationwide prospective cohort study that recruits new-onset T1D who are less than 18 years old at time of diagnosis. There are 40 pediatric medical centers (95% of pediatric centers in Sweden) from most parts of Sweden participating in the BDD study. The BDD study started recruiting new incident patients of T1D from May 1st, 2005 and is still ongoing. Children who are less than 18 years old at the time of diagnosis were included for the diagnosis will be confirmed based on clinical criteria and follow up after six months of onset. As of today, the BDD had recruited more than 3000 children and children developing diabetes during 2010 will also be recruited.
The diagnosis of T1D in the BDD is established according to the WHO 2003 Criteria for Diagnosis and Classification of Diabetes. For each newly diagnosed child, blood samples are collected within 3 days of diagnosis for specific risk testing of HLA genotyping and islet autoantibody assays. Assessment of the genetic risk is made through performing HLA DQA1 and B1 genotyping using the Polymerase Chain Reaction (PCR) on dried blood spots using allele-specific probes detected by time-resolved fluorescence. Genetic testing for HLA genotypes are performed at the Clinical Research Center (CRC) of Lund University, UMAS, Malmö. The official nomenclature of the HLA system of the Committee of the WHO is used. Blood samples are also used to test for the presence of islet autoantibodies (IAA, GAD65Ab, IA-2Ab and ZnT8-W-R-Q-Ab). Each participating clinic receives a remittance detailing the results of genetic and autoimmune markers from the CRC in Malmö.
At the same time blood samples are collected for biochemical and metabolic parameters, which are tested at the referring clinical center and a specific nurse-based questionnaire is filled. The questionnaire records demographical variables as well as clinical and family medical histories and also involves information about the patient’s origin for two generations. All questionnaire forms are reported to the National Registry of Childhood and Adolescents Diabetes (SWEDIABKIDS) at the Queen Silvia’s Children and Adolescents Hospital in Göteborg.
BDD is supported by grants from the National Institutes of Health (HLA typing and GAD65Ab and IA-2Ab) and from the BARNDIABETESFONDEN.
The Swedish Diabetes Registry