Red cell alloantibodies in 71,525 Malaysian blood donations: Predominance of anti‐Mia reflects GP .Mur‐associated antigenic diversity

Background and Objectives Red cell alloantibody prevalence in blood donors is generally low, but antibody profiles vary according to population antigenic distribution. Data from Southeast Asia remain limited, particularly for antibodies associated with the glycophorin (GP).Mur phenotype. Materials and Methods This retrospective cross‐sectional study analysed 71,525 voluntary whole blood donations at a tertiary hospital in Malaysia between 2019 and 2024. Donor demographic and laboratory data were retrieved from the laboratory information system. Antibody screening was performed using the indirect antiglobulin test with in‐house pooled screening cells incorporating Mi(a+). Positive samples underwent antibody identification using commercial panels. Univariable logistic regression was used to assess demographic determinants. Results Overall alloantibody prevalence was 0.4%. The most frequent specificities were anti‐Mia (19.1%) and anti‐M (17.5%). Among clinically significant antibodies, anti‐Mia accounted for 72.1% (49/68), followed by anti‐E, anti‐c, anti‐S and anti‐Diᵃ. Increasing age was associated with higher odds of alloantibody positivity. Discordant antibody profiles were observed in repeat donors, consistent with antibody evanescence. Conclusion Donor alloantibody epidemiology in Malaysia is characterized by a distinct spectrum dominated by anti‐Mia, reflecting GP.Mur‐associated antigenic diversity. Standard screening panels lacking Mi(a+)‐expressing cells may under‐detect clinically significant antibodies. Region‐specific screening strategies and strengthened haemovigilance systems are required to optimize transfusion safety in Southeast Asia.