Abstract: Objective To explore the accurate identification method of ABO subtypes, we analysed the serological and molecular biological features of three samples with B subtpye of the ABO blood group. Methods ABO phenotype of three samples were detected using traditional serological methods. The genotypes of Three samples were confirmed by DNA sequencing for exon 6, exon 7 and intron 3 at ABO locus . Results The serological phenotype of three samples were identified as B3,B3 and Bel. The genotype of sample 1 was identified as B303/O02 which with 5G>A mutation in intron 3. The genotypes of sample 2 and sample 3 were identified as Bx03/O01 which with 541 C>T mutation in exon 7 and Bel03/O02 which with 502 C>T mutation in exon 7, respectively. Conclusion ABO subtype can be accurately identified by combining serological and molecular biological method,and molecular biological methods are helpful to explore the mechanism of how ABO subtpyes generate.

Key words: ABO subtype, Serological test, Molecular biology, DNA sequencing