Population-based genetic screening for the estimation of Type 1 diabetes mellitus risk in Finland: selective genotyping of markers in the HLA-DQB1, HLA-DQA1 and HLA-DRB1 loci.

AIMS

To improve sensitivity and specificity of the diabetes risk assessment of the population-based genetic screening used in the Finnish Diabetes Prediction and Prevention (DIPP) trial.

METHODS

One thousand consecutive newborns enrolled in the DIPP were compared with 316 samples from children with Type 1 diabetes mellitus. A modification of the previously described technique based on hybridization of relevant PCR products with five lanthanide-labelled probes detected by time-resolved fluorometry (TRF) was used. A new probe was designed and allowed discrimination between DQB10602 and 0603 alleles, in addition to DQB102, *0301 or *0302, each of which required specific probes. A new, added screening strategy was developed for individuals carrying low-risk genotypes through specific typing of DQA1 05 and 0201 alleles in DQB102 positive, and DRB1 typing for DR4 subtypes in DQB10302 positive subjects, with a new specifically designed high-resolution TRF-based DR4 subtyping technique.

RESULTS

This two-step screening approach enhanced the sensitivity of the detection of genetic risk for Type 1 diabetes mellitus in this cohort up to 85.4%. In the general population cohort, 24.4% were identified for prospective follow-up, 2.6% of these are expected to develop Type 1 diabetes mellitus before the age of 15 years. Exclusive typing for HLA-DQB1 locus as an alternative screening strategy had sensitivities of 26.3-77.2% with general population cohorts of 2.3-23.1% identified for follow-up.

CONCLUSIONS

The described strategy for genetic prediction of Type 1 diabetes mellitus relies on the convenient genotyping procedure and could be applied in large scale screening projects such as DIPP.