RHD genotyping to resolve weak and discrepant RhD patient phenotypes.

Area of Science:

• Transfusion Medicine
• Genetics
• Immunology

Background:

• Implementing RHD genotyping in transfusion services for obstetrical patients and transfusion candidates.
• Addressing challenges with weak or discrepant automated microplate direct agglutination (MDA) RhD phenotypings.

Purpose of the Study:

• To examine how RHD genotyping resolves weak or discrepant RhD phenotypings.
• To assess the impact of RHD genotyping on the need for Rh Immune Globulin (RhIG) and D-negative Red Blood Cells (RBCs).

Main Methods:

• Investigated RhD phenotypes with equivocal or reagent-discrepant automated MDA, weak-2+ immediate-spin tube typings, historically discrepant RhD typings, or D+ typings with anti-D.
• Performed microarray RHD genotyping (RHD BeadChip).
• Managed patients as D+ with weak-D types 1, 2, and 3, and as D-negative with all other results.

Main Results:

• Weak-D prevalence was 0.14%. Among 138 patients, 38% had weak-D types 1, 2, or 3, 25% weak partial type 4.0, 21% other partial-D variant alleles, and 15% no variant detected.
• Discovered one novel allele with weak partial type 4.0 variants.
• RHD genotyping altered RhD management in 43% of patients, leading to a net conservation of D-negative RBCs and RhIG.

Conclusions:

• Equivocal or reagent-discrepant MDA RhD phenotypes are highly specific for weak-D or partial-D RHD genotypes.
• Resolution of RHD genotype status effectively reduced the utilization of D-negative RBCs and RhIG in the studied patient population.