How do we identify RHD variants using a practical molecular approach?

Area of Science:

• Immunogenetics
• Molecular Biology
• Transfusion Medicine

Background:

• Serologic discrepancies in RhD typing, particularly those involving partial D and weak D phenotypes, present challenges in routine blood banking.
• RHD genotyping offers superior characterization of RhD variants compared to traditional serologic methods.

Purpose of the Study:

• To develop and validate algorithms for identifying RhD variants in multiethnic populations.
• To establish a logic sequence of molecular tests for efficient and cost-effective RhD variant characterization.

Main Methods:

• Analysis of 360 blood samples exhibiting atypical D antigen expression.
• Utilized a multiplex polymerase chain reaction (PCR) procedure.
• Developed a six-flowchart algorithm incorporating PCR-restriction fragment length polymorphism and specific exon sequencing based on multiplex PCR results, RHCE allele, and D variant frequency.

Main Results:

• Successfully identified 22 distinct RhD variants using the developed algorithm with minimal assays and reduced cost.
• Demonstrated that comprehensive sequencing of all RHD exons is not essential for identifying most known D variants.

Conclusions:

• A practical and implementable algorithm for RHD genotyping has been established.
• The algorithm is adaptable to various ethnic backgrounds, requiring initial assessment of local D variant types and frequencies.
• This molecular strategy significantly improves the resolution of RhD discrepancies in transfusion medicine.