A Distinct Approach for Molecular ABO Typing: A Case of Serology–Genotype Discrepancy Within a Family

To the Editor, Accurate ABO blood group determination remains essential for safe transfusion practice.While serological methods constitute the standard approach in routine immunohematology, molecular techniques provide critical support when serologic typing is inconclusive or discordant.They are particularly valuable in cases of ABO variants, the presence of autoantibodies, recent transfusions with mismatched blood groups, weakened or lost antigen expression in hematologic malignancies, and in the identification of novel alleles.Here, we report the findings of a 7-year-old patient typed as A3 phenotype RhD positive.The parents-both physicians-raised concerns because a child with an A subgroup appears biologically incompatible with two parents declared as O RhD positive under Mendelian inheritance rules.This clinical discrepancy prompted a comprehensive serological and molecular evaluation of all three family members.Serologic testing was performed using automated gel centrifugation (Across RBC; Dia Pro), supplemented by anti-A1 and anti-H lectin testing.As shown in Figure 1, the results revealed a discrepancy characteristic of weak A subgroups.According to the specific criteria outlined in the National ABO Variant Reference Table of the National Blood and Blood Components Preparation, Use and Quality Assurance Guidelines [1], the A3 phenotype is explicitly defined by a characteristically weak or mixed-field reaction with Anti-A, a completely negative reaction with Anti-A1 lectin, and the the possible presence of anti-A1 antibodies in the reverse grouping.Consistent with these national reference criteria, our patient demonstrated strong positive reaction with anti-H lectin, a negative reaction with Anti-A1 lectin and a negative reverse grouping for Anti-A1 antibodies, thereby definitively confirming the diagnosis of the A3 phenotype.To further investigate, molecular ABO genotyping was performed using end-point fluorescent PCR (inno-train RBC-FluoGeneNX assays).The results, reported according to International u n c o r r e c t e d p r o o fstrategies, while this patient can molecularly synthesize A transferase, the lack of Anti-A1 antibodies provides a wider margin of safety, though a cautious approach is still warranted.To maximize transfusion safety and prevent potential adverse reactions, it is clinically recommended that this individual receives Group O packed red blood cells (RBCs) [1,8].By integrating molecular workflows into routine laboratory management, clinical centers can significantly reduce turnaround time and operator dependency, moving beyond the mere resolution of biological discrepancies toward proactive, personalized transfusion safety.