Transfusion strategy for weak D Type 4.0 based on RHD alleles and RH haplotypes in Tunisia

Area of Science:

• Immunogenetics
• Blood group serology
• Population genetics

Background:

• The RHD gene is highly polymorphic, with over 460 alleles, making it the most complex blood group system.
• Tunisia exhibits a high prevalence of weak D Type 4.0 alleles, affecting 1 in 105 RH haplotypes.

Purpose of the Study:

• To investigate the prevalence and characteristics of weak D phenotypes in the Tunisian population.
• To establish a transfusion strategy for individuals with weak D Type 4.0 in Tunisia.

Main Methods:

• Screening of 13,431 Tunisian blood donations for serologic weak D phenotype.
• Sequencing of the RHD coding sequence and introns.
• RHCE gene analysis to determine RH haplotypes.

Main Results:

• A weak D phenotype was identified in 0.50% (67/13,431) of donors.
• Weak D Type 4 alleles accounted for nearly 90% of weak D phenotypes, with Type 4.0 being the most frequent (88% of weak D Type 4).
• Specific RHCE alleles were commonly associated with different RHD variants, such as RHCE*ceVS.04.01 with weak D Type 4.0.

Conclusions:

• Weak D Type 4.0 is the predominant weak D allele in Tunisia.
• No novel RHD alleles were identified.
• Based on established haplotypes and the absence of adverse clinical events, RhD-positive (D+) transfusions are recommended for patients with weak D Type 4.0 in Tunisia.