Serological Phenotyping and Molecular Blood Group Genotyping for Erythrocyte Antigen Characterization and Alloimmunization Assessment in Sickle Cell Anemia
Ana Kélvia Araújo Arcanjo *
Graduate Program in Biotechnology – PPGBIOTEC, Ceará, Brazil.
Ivina Rhaissy Ximenes de Mesquita
School of Pharmacy, Centro Universitário INTA – UNINTA, Sobral, Ceará, Brazil.
Francisco Kauê Carvalho Aguiar
School of Pharmacy, Centro Universitário INTA – UNINTA, Sobral, Ceará, Brazil.
Luana Araujo Arcanjo
School of Medicine, Centro Universitário INTA – UNINTA, Sobral, Ceará, Brazil.
Deivide de Sousa Oliveira
School of Medicine, Centro Universitário INTA – UNINTA, Sobral, Ceará, Brazil.
Alaíde Maria Rodrigues Pinheiro
School of Medicine, Centro Universitário INTA – UNINTA, Sobral, Ceará, Brazil.
José Jackson do Nascimento Costa
School of Medicine, Centro Universitário INTA – UNINTA, Sobral, Ceará, Brazil.
*Author to whom correspondence should be addressed.
Abstract
Background and Aims: Red blood cell (RBC) transfusion is essential in sickle cell anaemia (SCA), but alloimmunisation can complicate transfusion support. To evaluate the contribution of molecular blood group genotyping to erythrocyte antigen characterization and alloimmunization assessment in patients with sickle cell anemia (SCA) from Northeastern Brazil.
Study Design: Retrospective observational study with cross-sectional molecular characterization.
Place and Duration of Study: Hemoglobinopathies Outpatient Clinic of the Regional Blood Center of Sobral (HEMOCE), Ceará, Brazil, from February 2017 to July 2026.
Methodology: We conducted a retrospective, record-based study with cross-sectional molecular characterization of 50 patients with HbSS. Extended serologic phenotyping and molecular genotyping were integrated to characterize clinically relevant blood group systems. Population-level phenotype–genotype correspondence, RHCE diversity, FY*B_GATA-mediated erythroid silencing, alloantibody profiles, and selected factors potentially associated with alloimmunization were evaluated.
Results: RBC alloantibodies with identified specificities were detected in 13 of 50 patients (26.0%), predominantly involving Rh and Kell antigens. Serologic and genotype-predicted antigen frequencies showed close population-level correspondence for directly comparable antigens (Pearson’s r = 0.995, p < 0.001). In the Duffy system, serologic Fyᵃ and Fyᵇ positivity was observed in 68.0% and 58.0% of patients, respectively, and the FY*B_GATA regulatory variant was identified in 21 patients (42.0%), enabling molecular interpretation of erythroid-specific Fyᵇ silencing. Molecular genotyping also provided additional characterization of RHCE diversity, including the variant-associated antigens V and VS and the high-incidence antigens hr^S and hr^B. In exploratory analyses, no significant associations were observed between alloimmunization and Rh E, VS, or FY*B_GATA after restricting the outcome to patients with identified RBC alloantibodies.
Keywords: Sickle cell anemia, blood group antigens, genotyping techniques, isoantibodies, Rh-Hr blood-group system