SI35 Blood Group Antigen Typing Using DNA Microarray BeadChipsTM–First UK Report

Background  The determination of human blood group phenotypes has routinely involved red cell agglutination techniques. The genes for all but one of the 29 human blood group systems have now been cloned and the molecular bases of all clinically significant blood group polymorphisms are known. Consequently these DNA sequences can be used to predict blood group phenotypes. Molecular typing as an adjunct to serology offers improved accuracy and can save both rare reagents and laboratory time while screening for compatible donor units. This study determined the feasibility of analysis of single nucleotide polymorphisms (SNPs) associated with a variety of blood group antigens using a DNA microarray system with a beadchip technology platform. Method  SNPs were tested by elongation-mediated analysis of polymorphisms (eMAPTM) using allele-specific oligonucleotides with variable 3’-terminal sequences attached to colour-encoded beads. The beads are assembled into arrays on semiconductor chips (BeadChipTM), available from Bioarray Solutions. Elongation products for SNPs or small deletions/insertions were simultaneously detected by instant imaging of fluorescence signals from the entire array. Seventeen polymorphisms associated with Human Erythrocyte Antigens and one mutation associated with hemoglobinopathies (CO, DI, DO, FY, JK, KEL, LU, LW, MNS, SC and HgbS) were included in the HEA BeadChipTM Kit. Results  The system was validated using a reference DNA panel of known phenotype (n = 30) and genotype, established by conventional DNA-PCR SSP assays. Replicate testing (n = 6 reps for eight samples) gave 100% consistent data demonstrating the Bioarray system to be both reliable and reproducible. The initial concordance rate with serology was 99.2%. Conclusion  The BeadChip System represents the first integrated flexible array solution for high complexity transfusion testing, accommodating ‘multiplex’ analysis of polymorphisms. This high throughput, microarray system offers the potential to determine extended genotypes of patients and maintain an extended-genotype, national panel of donors to provide compatible blood for sensitised patients. The initial high concordance rate and the rarity of CE marked phenotyping reagents justifies its further development.