Abstract: Objective Serological and gene sequencing methods were performed on 4 samples with the ABO discrepancy to accurately determine blood type. Methods Samples suspected of subtype A detected by serological testing were subjected to Sanger bidirectional sequencing, and the genotypes and phenotypes were analyzed via software-assisted analysis and comparison. Results The gene sequence of two out of four samples was consistent with ABO*AEL.08/ABO*O.01.01 and ABO*AEL.03/ABO*B.02, respectively, both exhibiting the A_el phenotype. One sample was identified as ABO*AW.37/ABO*B.01, corresponding to the A_weakB type. A heterozygous mutation of 287G>T was detected in exon 6 in one case. This mutation is not documented in the ISBT database and is suspected to represent a novel mutation site on the ABO*A1.02 allele. Conclusion Serology in conjunction with molecular biological detection can facilitate a more accurate assessment of samples that exhibit ABO discrepancy to ensure the safety and efficacy of blood transfusions. The serological characteristics and gene sequence analysis of samples with diminished A antigen expression, can provide valuable data support for the identification of subtype A.

Key words: Weak A antigen, A subtype, Gene locus mutation, Molecular sequencing