title: RHD variants in Flanders, Belgium.
abstract: BACKGROUND
  D antigen variants may be grouped into partial D, weak D, and DEL types. Cumulative phenotype frequencies of these D variants may approach 1% in certain European regions. Unambiguous and quick identification of D variants is of immediate clinical relevance, with implications for transfusion strategy.
  
  
  METHODS
  A total of 628 samples with ambiguous serologic results from different immunohematology laboratories throughout the Flanders region, Belgium, were genotyped using a commercially available weak D typing approach. After exclusion of detectable weak D types, molecular RHD exon scanning was performed for the remaining samples, and RHD sequencing was performed in two particular cases.
  
  
  RESULTS
  Of all samples investigated, 424 (67.5%) were positive for weak D Type 1, 2, or 3, and 22 cases (3.5%) typed weak D Type 4.0/4.1/4.3, 4.2, 5, 11, 15, or 17. Another 49 (7.8%) samples were partial D variants, with a major proportion being category DVI types (n = 27). One RHD(S103P) sample was identified as high-grade partial D, with DIII-like phenotype and anti-D and anti-C immunization. Additionally, a novel DVI Type 3 (A399T) variant was found. Of the remaining 133 samples mainly tested because of ambiguous serologic D typing results due to recent transfusion, 32 (5.1%) were negative for RHD, and 101 (16.1%) were indistinguishable from wild-type RHD and not investigated further.
  
  
  CONCLUSIONS
  Despite the enormous diversity of RHD alleles, first-line weak D genotyping was remarkably informative, allowing for rapid classification of most samples with conspicuous RhD phenotype in Flanders. The clinical implications are discussed.
authors.affiliation: Histocompatibility and Immunogenetic Laboratory, Red Cross Flanders, Mechelen, Belgium.
authors.forename: Vicky S T
authors.initials: VS
authors.lastname: Van Sandt
authors.affiliation: Blood Transfusion Service Zürich, Swiss Red Cross, Schlieren, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gassner
authors.affiliation: Histocompatibility and Immunogenetic Laboratory, Red Cross Flanders, Mechelen, Belgium.
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Emonds
authors.affiliation: Department of Transfusion Medicine, University of Göttingen, Göttingen, Germany.
authors.forename: Tobias J
authors.initials: TJ
authors.lastname: Legler
authors.affiliation: Histocompatibility and Immunogenetic Laboratory, Red Cross Flanders, Mechelen, Belgium.|ZNA Stuivenberg, Antwerp, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Mahieu
authors.affiliation: Department of Blood Group Serology and Transfusion Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Günther F
authors.initials: GF
authors.lastname: Körmöczi
mesh_terms: D000483:Alleles; D001530:Belgium / Q000453:epidemiology; D001782:Blood Donors / Q000706:statistics & numerical data*; D001788:Blood Grouping and Crossmatching / Q000706:statistics & numerical data; D018604:Epitope Mapping; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007518:Isoantibodies / Q000097:blood; D008969:Molecular Sequence Data; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D012204:Rh-Hr Blood-Group System / Q000235:genetics* / Q000276:immunology; D018029:Rho(D) Immune Globulin
chemical_list: D007518:Isoantibodies; C061961:RHO(D) antibody; D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin; C026410:Rho(D) antigen