Screening for the IDDM high-risk genotype. A rapid microtitre plate method using serum as source of DNA

Norwegian babies born with the HLA-DRB1*0401-DQA1*03-DQB1*0302/DRB1*03-DQA1+ ++*05-DQB1*0201 genotype have an estimated 17% lifetime risk of developing insulin-dependent diabetes mellitus (IDDM). Identifying these children is important for future prevention, and for studies of the non-genetic factors involved in IDDM. The aim of the study was to develop a rapid screening method for this high-risk genotype. DNA was extracted from serum collected during routine newborn screening for phenylketonuria and hypothyreosis. The second exons of HLA-DQA1 and DQB1 were co-amplified using biotinylated primers, amplicons were hybridized to a set of seven probes immobilized on a microtitre plate using a single hybridisation temperature, and detected colorimetrically by streptavidin-HRP conjugate and tetramethylbenzidine substrate. The DRB1*04 subtyping was performed using six different probes at identical conditions. The prevalence of the DRB1*0401-DQA1*03-DQB1*0302/DRB1*03-DQA1*0 5-DQB1*0201 genotype among 1,026 Norwegian babies was 2.7% (CI 95%: 1.7-3.7%). The new high-throughput genetic screening method for IDDM risk can easily be automated and included in newborn screening programs.