RESUMEN
【Objective】 To investigate the serology and genotype identification method of B (A) subtype patients. 【Methods】 Test tube method (serology) was used to confirm the clinically difficult ABO blood group samples of 3 patients with ABO blood group; ABO blood group was genotyped by real-time PCR, and the ABO gene exon 1-7 was sequenced to determine the genotype. 【Results】 The forward and reverse blood typing result of three patients was B (A) subtype all with ABO genotype B/O2 and c.640A> G mutation on B allele of exon 7, which meets the characteristics of ABO * BA.04 genotype. 【Conclusion】 The combination of serological and genetic testing could identify difficult blood types such as ABO subtypes accurately and ensure the safety of clinical blood use.