title: Weak D phenotypes and transfusion safety: where do we stand in daily practice?
abstract: BACKGROUND
  Weak D Types 1, 2, and 3 recipients cannot be immunized when exposed to D antigen. Molecular biology is very efficient to type weak D variants but rarely implemented in daily practice. The serologic typing practice of weak D in a Caucasian patient population was analyzed and a transfusion strategy is proposed.
  
  
  METHODS
  Samples typed either ddCcee or ddccEe in routine laboratories were tested with the indirect antiglobulin test (D(u) test). D(u)-positive samples were screened for weak D alleles Types 1, 2, and 3 and further tested with immunoglobulin M (IgM) anti-D reagents, used in a fully automated device.
  
  
  RESULTS
  A total of 468 of 55,162 samples were found to be ddCcee or ddccEe. Ninety-three expressed weak D after the D(u) test leading to D+ assignment for transfusion. Seventy-three percent of D(u)-positive samples were weak D alleles Type 1, 2, or 3. Almost all weak D Types 1, 2, and 3 were positive with IgM reagents in gel matrix with an automated device. Other variants that could be potentially associated with anti-D alloimmunization, however, were also positive.
  
  
  CONCLUSIONS
  Serology is very sensitive to detect weak D Types 1, 2, and 3, but there is no cutoff to distinguish variants of clinical significance. When molecular analysis is not available, it is proposed that a D+ status for blood recipients found to be weak D with a sensitive method be assigned, except for women of childbearing age or younger, because of the remaining possibility to be partial D or other rare weak D who can be immunized.
authors.affiliation: French Blood Establishment, Island of France, Créteil, France. france.noizat-pirenne@efs.sante.fr
authors.forename: France
authors.initials: F
authors.lastname: Noizat-Pirenne
authors.forename: Martine
authors.initials: M
authors.lastname: Verdier
authors.forename: Annette
authors.initials: A
authors.lastname: Lejealle
authors.forename: Anne
authors.initials: A
authors.lastname: Mercadier
authors.forename: Philippe
authors.initials: P
authors.lastname: Bonin
authors.forename: Françoise
authors.initials: F
authors.lastname: Peltier-Pujol
authors.forename: Anne
authors.initials: A
authors.lastname: Fialaire-Legendre
authors.forename: Christophe
authors.initials: C
authors.lastname: Tournamille
authors.forename: Philippe
authors.initials: P
authors.lastname: Bierling
authors.forename: Hélène
authors.initials: H
authors.lastname: Ansart-Pirenne
mesh_terms: D000483:Alleles; D001331:Automation; D001788:Blood Grouping and Crossmatching / Q000379:methods* / Q000592:standards*; D001803:Blood Transfusion / Q000379:methods* / Q000592:standards*; D018604:Epitope Mapping; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D007202:Indicators and Reagents; D010641:Phenotype; D012204:Rh-Hr Blood-Group System / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D012680:Sensitivity and Specificity; D012698:Serologic Tests
chemical_list: D007075:Immunoglobulin M; D007202:Indicators and Reagents; D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen