Abstract: Objective To investigate the gene identification of a patient with serologic blood group discrepancy, and analyze the reason and variations. Methods Microcolumn agglutination and routine tube method were used for serologic blood group identification, and Coombs' and antibody screening were performed. Exon 6,7 and their adjacent intron region of ABO gene were amplified by polymerase chain reaction (PCR), and the PCR products were directly sequenced to identify the gene mutation. Results The forward and reverse tests of serologic blood group identification were not consistent. The red blood cells of the patient showed weak positive(++) with monoclonal anti-A and positive(++++) with monoclonal anti-B and anti-H. The patient's serum showed weak agglutination with type A1 red blood cells and no agglutination with type B and type O red blood cells. The direct and indirect Coombs and antibody screening were all negative. There were 2 heterozygous variations in exon 6 (261del and c.297A>G) and 11 heterozygous variations in exon 7 (c.526C>G, c.640A>G, c.646T>A, c.657C>T, c.681G>A, c.703G>A, c.771C>T, c.796C>T, c.803G>C, c.829G>A and c.930G>A) of ABO gene in the patient compared with the reference sequence of A101 allele. Based on the Blood Group Antigen Gene Mutation Database, B(A)04/O06 subgroup alleles were identified. Conclusions The variation of B allele and the weak AB phenotype are the main reasons of the discrepancy in blood group identification for the patient. DNA genotyping could help us with solving the blood group identification for complicated serologic discrepancy samples.

Key words: ABO subgroup, B(A) blood group, Genotype, Allele