Three novel RHD variant alleles were identified through routine molecular screening of serologically RH1 negative first-time blood donors.

BACKGROUND

The RH blood group system, particularly the RH1 (D) antigen, is highly immunogenic and clinically significant in transfusion medicine. Standard serological donor RH1 typing may fail to detect very weakly expressed RH1 variants, resulting in a risk of alloimmunization in recipients negative for the corresponding antigen. In 2012, routine molecular screening of RH1-negative first-time donors was implemented in Switzerland to improve transfusion safety. In this context, we present three novel RH1 variant alleles discovered through molecular analysis.

METHODS

Serological RH phenotyping was performed using column agglutination, adsorption-elution testing, and monoclonal antibody panels. Genomic DNA and RNA were extracted and analyzed by SSP-PCR, RHD exon sequencing, and cDNA sequencing.

RESULTS

Three previously undescribed RHD variant alleles were identified in four first-time donors. Two donors carried a nonsense mutation NM_016124.5:c.265C>T resulting in a premature stop codon (NP_057208.2:p.Gln89Ter), associated with an apparent RH1-negative phenotype but weakly positive adsorption-elution results. One donor carried a missense mutation NM_016124.5:c.863 T>A (NP_057208.2:p.Ile288Asn), associated with extremely weak RH1 expression. In one donor with a true RH1-negative phenotype, a frameshift mutation NM_016124.5:c.970del was identified, resulting in NP_057208.2:p.His324Thrfs*35 and predicted truncation of the RH1 protein.

DISCUSSION: The findings demonstrate that routine molecular RHD screening of serologically RH1-negative first-time donors is essential for the detection of rare RHD variants that may escape serological testing. Molecular characterization of such alleles improves transfusion safety by preventing inadvertent transfusion of RH1-positive red blood cells to RH1-negative recipients and contributes to a more comprehensive understanding of RHD genetic diversity.