Serology and gene sequence analysis of the B(A) subtype of patients in Hunan

B(A) is a relatively rare ABO subtype. The frequency of B(A) in European Caucasians is low, but is higher in China. B(A) is common in northern China, gradually decreasing from north to south. The frequency of B(A) has been researched in northern China, but not in southern China. This study aimed to investigate the serological characteristics and molecular mechanism of the B(A) subtype in Hunan.The phenotypes of ABO blood group were analyzed by blood group serology for the patients in the Third Xiangya Hospital from 2016 to 2020; Exons 1-7 of the ABO gene were screened by PCR-SSP and sequencing.Nine cases were suspected as belonging to the B(A) subtype by serological tests. The activity of D-galactosyltransferase in these patients' serum was significantly higher than that of group B plasma; meanwhile, there was no activity of Nacetylgalactosyltransferase. The ABO genotype was ABO*B.01/O.01.01 or ABO*B.01/O.01.02, and the gene sequencing results confirmed the phenotype as B(A), whose gene frequence was 1/26,000. Allele ABO*BA.02 (1/38,000) had the highest frequency, followed by ABO*BA.04 (1/77,000).Among the patients in Hunan, the most common allele encoding the B(A) phenotype was ABO*BA.02. The identification of the B(A) blood group required serological methods combined with genotyping.