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Oral Abstract

Immunohematology and Genetic Testing (red cells/leukocytes and platelets) - Molecular Diagnostics and Testing

Oral Abstract Session - Novel RHD Variants and Approaches to Overcoming Them

#OA2-AM25-MN-36 - Molecular Characterization of Variant D Antigen Expression Among 56,445 Blood Donors in East India

Monday, October 27, 2025
5:00 PM - 6:00 PM  PT
Room: SDCC 30CDE
Oral Abstracts
Background/Case Studies: Transfusion of red cells from RhD-positive donors to recipients lacking all or some epitopes of the D antigen can lead to the development of anti-D, potentially resulting in hemolytic transfusion reactions. Over 500 RHD alleles affect the qualitative or quantitative expression of the D antigen. There are huge differences in their prevalence among populations. Despite the distinct genetic diversity across multiple sub-populations in India, the prevalence of RHD alleles among the more than 270 million people in the East Indian region remained unknown.

Study

Design/Methods: EDTA-anticoagulated whole blood samples were collected between 1st January 2021 and 30th September 2024. The blood donors came from different districts of West Bengal and adjacent states in East India. Standard hemagglutination tests were performed for D antigen typing. Molecular tests were performed using commercial genotyping kit (Inno-Train Diagnostik, Hessen, Germany), next generation or Sanger sequencing.

Results/Findings: Over 3 years, 56,445 blood donors were tested at the Tata Medical Center, Kolkata by serology. Among these donors, 2,421 were confirmed as D-negative (4.3%), while 23 (0.04%) showed discrepant D-typing with weak reactions during the immediate spin test, all of them were C+. Variant RHD alleles were identified in 15 samples (15/23, 65.2%). The Indian-type weak D (RHD*01W.150) was the most common variant (30.4%, n=7), occurring in 1 in 8,063 blood donors in East India versus 1 in 729 blood donors in South India (p < 0.001). Other identified variants included RHD*06.03.01 (n=3), RHD*17.05 (n=2), RHD*01.EL.37 (n=2), and RHD*01W.96 (n=1). The remaining 8 samples (8/23, 34.8%) carried the reference RHD allele (RHD*01.01).

Conclusions: Our findings reveal a lower prevalence of Indian-type weak D in East India than South India, indicating region-specific genetic diversity. The higher incidence of weak or variant D individuals with the wild-type RHD allele in our East Indian cohort suggests the potential presence of an unknown region-specific molecular variant, possibly located in the untranslated regions of the RHD gene. No proper DEL allele has been found so far in the large Indian population, in striking difference to East and Southeast Asia. While RHD*06.03.01 and RHD*17.05 have, the 3 others identified RHD alleles have not been associated with anti-D alloimmunization. We recommend D-negative transfusion as a precautionary measure for patients with D-variants in East India. Our study helps define the boundaries of Asian-type DEL allele distribution, which will ultimately inform the care of U.S. patients who trace their ancestry to South Asia versus Southeast and East Asia.