Background/Case Studies: In East and Southeast Asia, D-negative blood units and donors are rare (< 0.5%). The Del phenotype is a rare variant of the D antigen in the Rh blood group system. Del red cells carry an extremely low number of D antigens on their surface, undetectable by any routine serologic methods and thus type as D-negative. Clinical trials and retrospective data suggest that patients with the Asian-type DEL (RHD*DEL1) can be safely managed as D-positive. However, despite a clinically relevant prevalence of Asian-type DEL (typically 17%) in East Asia, data on its prevalence in the Malay population were lacking.
Study
Design/Methods: Rh phenotyping records of all blood donors from Terengganu, Malaysia, between January 2020 and July 2024, including Malay, Chinese and Indian ethnicity, were reviewed. RHD genomic screening was performed on serologically D-negative blood donor and patient samples between March and July 2024. We screened for RHD intron 4, exon 5, and exon 7, identified Asian-type DEL by real-time PCR, and other variant RHD alleles by a genotyping kit or nucleotide sequencing.
Results/Findings: Among all blood donors, 0.53% were serologic D-negative (179/33,829). We detected 5 distinct RHD alleles that cause the serologic D-negative phenotype among the 32 D-negative donors and 40 patients. The unbiased estimate of Asian-type DEL was 28% among donors and 18% among patients. Conclusions: The prevalence of Asian-type DEL in the Malay population exceeded most prevalences in East Asia, which affects current thinking about Asian-type DEL in Southeast Asian populations. Implementing red cell genotyping can improve the precise allocation of red cell resources, conserve the supply of rare D-negative blood, and reduce costs by eliminating unnecessary RhIG injections. We discuss a change in transfusion practice and propose to introduce a D-positive management for patients and pregnant woman with the Asian-type DEL in Malaysia, which may guide the implementation in other Southeast Asian countries. This novel approach will eventually transform and have positive impact on the care of the U.S. patients who trace their ancestry to East and Southeast Asia.
