title: Citrate-dependent auto-antibody causing error in blood grouping.
abstract: OBJECTIVE
  Errors in blood grouping are occasionally due to anomalous antibodies or extraneous materials in the reagents. We investigated the case of a volunteer blood donor who was originally grouped as AB, Rh-positive, by slide grouping. However, her washed red cells showed group B, which agreed with her reverse serum grouping.
  
  
  METHODS
  Standard serologic techniques were employed throughout.
  
  
  RESULTS
  Investigation revealed an unusual autoantibody in the donor's blood that preferentially agglutinated the red cells in the presence of citrate. Because the grouping reagents contained citrate, this led to a false grouping when whole blood was tested rather than washed red cells. The antibody reacted at 37 degrees C and at 4 degrees C, but failed to agglutinate red cells when 0.1 M solution of monosaccharides was added to the reaction mixture. The antibody agglutinated all red cells except 6 examples of the 'Bombay' phenotype included in the panel. The antibody was neutralized by H secretor saliva, and its activity was abolished by DTT reagent, indicating its possible IgM nature.
  
  
  CONCLUSIONS
  These findings suggest that this anomalous antibody has anti-H specificity.
authors.affiliation: Surat Raktadan Kendra, India.
authors.forename: S R
authors.initials: SR
authors.lastname: Joshi
mesh_terms: D000017:ABO Blood-Group System / Q000032:analysis* / Q000276:immunology; D016477:Artifacts; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D001782:Blood Donors; D001788:Blood Grouping and Crossmatching / Q000379:methods*; D001800:Blood Specimen Collection / Q000379:methods*; D002951:Citrates / Q000494:pharmacology*; D005189:False Positive Reactions; D005260:Female; D005643:Fucose / Q000276:immunology; D006388:Hemagglutinins / Q000097:blood* / Q000276:immunology; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology; D008875:Middle Aged; D009005:Monosaccharides / Q000494:pharmacology; D000077559:Sodium Citrate
chemical_list: D000017:ABO Blood-Group System; D001323:Autoantibodies; D002951:Citrates; D006388:Hemagglutinins; D007075:Immunoglobulin M; D009005:Monosaccharides; D000077559:Sodium Citrate; D005643:Fucose