<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>The D antigen is highly immunogenic and may cause allo-immunization to occur after blood transfusion or pregnancy. Some <italic>RHD</italic> variant alleles express a D antigen that is missing one or more epitopes, thus putting a presumed D+ patient at risk for alloanti-D and hemolytic disease of the fetus and newborn. It is generally accepted that individuals who have a serologic weak D phenotype due to one of three alleles common in Caucasians, <italic>RHD*weak D types 1, 2</italic>, or <italic>3</italic>, are not at risk for alloimmunization. In this study, blood samples from 46 obstetrics patients from a local health system were identified based on discrepant results between automated gel and manual tube testing (<italic>n</italic> = 20) or based on presentation with a serologic weak D phenotype (<italic>n</italic> = 26). <italic>RHD</italic> genotyping was performed using commercial and laboratory-developed tests. Of the 26 serologic weak D samples, 18 (69.2%) were found to carry alleles <italic>RHD*weak D type 1, 2</italic>, or <italic>3.</italic> The remaining eight samples (30.8%) were found to carry partial D alleles. Of the 20 samples submitted because of D typing discrepancy, 7 (35%) carried alleles <italic>RHD*weak D type 1, 2</italic>, or <italic>3</italic>, while 13 (65%) carried partial <italic>RHD</italic> alleles. This report summarizes the findings of one hospital system and its approach to integrating <italic>RHD</italic> genotyping into its assessment of risk of alloimmunization in obstetrics patients. It demonstrates that individuals with partial <italic>RHD</italic> alleles can present with serologic weak D phenotype, such that, without <italic>RHD</italic> genotyping, these individuals may not be identified as candidates for Rh immune globulin. The study also demonstrates that use of two methods (automated gel and tube testing) allows for identification of partial D cases that would otherwise be missed.</p>
</abstract>

The D antigen is highly immunogenic and may cause allo-immunization to occur after blood transfusion or pregnancy. Some RHD variant alleles express a D antigen that is missing one or more epitopes, thus putting a presumed D+ patient at risk for alloanti-D and hemolytic disease of the fetus and newborn. It is generally accepted that individuals who have a serologic weak D phenotype due to one of three alleles common in Caucasians, RHD*weak D types 1, 2, or 3, are not at risk for alloimmunization. In this study, blood samples from 46 obstetrics patients from a local health system were identified based on discrepant results between automated gel and manual tube testing (n = 20) or based on presentation with a serologic weak D phenotype (n = 26). RHD genotyping was performed using commercial and laboratory-developed tests. Of the 26 serologic weak D samples, 18 (69.2%) were found to carry alleles RHD*weak D type 1, 2, or 3. The remaining eight samples (30.8%) were found to carry partial D alleles. Of the 20 samples submitted because of D typing discrepancy, 7 (35%) carried alleles RHD*weak D type 1, 2, or 3, while 13 (65%) carried partial RHD alleles. This report summarizes the findings of one hospital system and its approach to integrating RHD genotyping into its assessment of risk of alloimmunization in obstetrics patients. It demonstrates that individuals with partial RHD alleles can present with serologic weak D phenotype, such that, without RHD genotyping, these individuals may not be identified as candidates for Rh immune globulin. The study also demonstrates that use of two methods (automated gel and tube testing) allows for identification of partial D cases that would otherwise be missed.

Identifying obstetrics patients in whom <italic>RHD</italic> genotyping can be used to assess risk of D alloimmunization

Immunohematology

Identifying obstetrics patients in whom  genotyping can be used to assess risk of D alloimmunization

The D antigen is highly immunogenic and may cause allo-immunization to occur after blood transfusion or pregnancy. Some RHD variant alleles express a D antigen...

Identifying obstetrics patients in whom RHD genotyping can be used to assess risk of D alloimmunization

Article Category: article

Published Online: Jan 01, 2020

Page range: 146 - 151

DOI: https://doi.org/10.21307/immunohematology-2020-054

Keywords
D, blood group antigen, genotyping, pregnancy, alloimmunization, RhIG prophylaxis, hemolytic disease of fetus and newborn (HDFN)

© 2020 T.N. Horn et al., published by Sciendo