title: How I manage donors and patients with a weak D phenotype.
abstract: OBJECTIVE
  Since the adoption of molecular blood-group typing, the considerable heterogeneity of the serologic entities weak D and DEL at the molecular level has come to light. I offer an approach to the management of donors and patients expressing D antigen weakly and carrying any of the various molecular types of weak D and DEL.
  
  
  RESULTS
  More than 50 distinct weak D alleles have been described. An internet-based survey of anti-D immunizations occurring in D-positive transfusion recipients reveals that no allo-anti-D has been observed in patients carrying prevalent weak D types. Allo-immunizations are documented for weak D types 4.2 (also known as DAR), 11 and 15. Anti-D immunizations have been reported in D-negative persons transfused with weak D and DEL red blood cells.
  
  
  CONCLUSIONS
  Patients carrying any of the prevalent weak D types 1, 2, 3 or 4.1 are not prone to allo-anti-D immunization and may safely be transfused with D-positive red blood cells. Pregnant women with these weak D types need not receive RhIg. We should pay attention to weak D- or DEL-positive blood units that are labelled D-negative. The clinical benefit of removing DEL blood units from our supply of D-negative red blood cell units should be determined.
authors.affiliation: Institute for Clinical Transfusion Medicine and Immunogenetics, Ulm, Germany. willy.flegel@uni-ulm.de
authors.forename: Willy A
authors.initials: WA
authors.lastname: Flegel
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001782:Blood Donors; D001788:Blood Grouping and Crossmatching / Q000379:methods*; D002678:Chimera; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D012204:Rh-Hr Blood-Group System / Q000032:analysis* / Q000097:blood / Q000235:genetics; D012680:Sensitivity and Specificity
chemical_list: D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen