Suwat Chiawchan, MSc¹ , Sukanlayanee Onseedaeng, MSc¹ , Panitita Suksomboonvong, MSc¹ , Pimpun Kitpoka, MD¹ , Pasuporn Po-ngernnak, MD, PhD¹

Background: Blood group antigens are polymorphic, and their immunogenicity has the potential for alloimmunization. Traditionally, serologic red blood cell (RBC) phenotyping is performed in the transfusion service to identify antigen-matched RBCs between donors and patients for safe transfusion. An inaccuracy of RBC phenotyping has been observed due to the limitations of the classical hemagglutination method. Genotyping has recently been introduced to tackle the difficulty of serological phenotyping.

Objective: To observe the discrepancy between phenotype and genotype in both donors and thalassemic patients.

Materials and Methods: A cross-sectional study was conducted between December 2018 and 2019, targeting Thai blood donors who donated blood at least twice a year at the Blood Bank, Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, and Thai transfusion-dependent thalassemic patients who had received blood from the Blood Bank. Forty-two blood donors and 66 multiple-transfused thalassemic patients were included in this study. Two blood samples of each donor and patient were used, one for serological RBC phenotype and the other for the BLOODchip® molecular analysis. A comparison between phenotype and genotype was carried out for Rh (C, c, E, e), Kidd (Jk(a), Jk(b)), Duffy (Fy(a), Fy(b)), and MNS (M, N, S, s, Mi(a)) systems.

Results: Twenty-four out of 66 (36.36%) patients showed discordance between phenotyping and genotyping results. A phenotype+/genotype– pattern was more common among thalassemic patients, with the discrepancies occurring most frequently in the Duffy and MNS systems. Among the 42 donors, only one individual (2.38%) demonstrated a discordant result, also in the Duffy system.

Conclusion: The discrepancies between phenotype and genotype were seen in both donors and patients. The patients with the phenotype+/genotype– had a potential for alloimmunization. Blood group genotyping has the benefit over serologic phenotyping, particularly in the thalassemic patients who require lifelong regular transfusion.

Received 24 December 2025 | Revised 29 April 2026 | Accepted 8 May 2026

J Med Assoc Thai 2026;109(11):855-63

DOI: 10.35755/jmedassocthai.2026.11.04040