title: Acute extravascular hemolytic transfusion reaction due to anti-Kpa antibody missed by electronic crossmatch.
abstract: BACKGROUND
  Kpa antigen is a low incidence red blood cell antigen within the Kell system. Anti-Kpa alloantibody may be associated with acute and delayed hemolytic transfusion reactions.
  
  
  METHODS
  We report a case of a clinically significant acute extravascular hemolytic transfusion reaction mediated by previously unrecognized (and undetected) anti-Kpa alloantibody. This reaction occurred in a patient who met all criteria for electronic crossmatch, resulting in the transfusion of an incompatible red cell unit.
  
  
  RESULTS
  Post-transfusion investigation showed the transfused red cell unit was crossmatch compatible at the immediate spin phase but was 3 + incompatible at the antiglobulin phase. No evidence of intravascular hemolysis was observed upon visual comparison of the pre- and post-transfusion peripheral blood plasma. Further testing showed the presence of anti-Kpa antibody. The clinical course of the patient included acute febrile and systemic reaction.
  
  
  CONCLUSIONS
  Acute extravascular hemolytic transfusion reaction may occur due to undetected anti-Kpa alloantibody. Various strategies for crossmatching are discussed in the context of antibodies to low incidence antigens.
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada. Electronic address: rpadmore@ottawahospital.on.ca.
authors.forename: Ruth
authors.initials: R
authors.lastname: Padmore
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Philip
authors.initials: P
authors.lastname: Berardi
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Kathy
authors.initials: K
authors.lastname: Erickson
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Diana
authors.initials: D
authors.lastname: Desjardins
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Antonio
authors.initials: A
authors.lastname: Giulivi
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Melanie
authors.initials: M
authors.lastname: Tokessy
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Doris
authors.initials: D
authors.lastname: Neurath
authors.affiliation: Division of Hematopathology and Transfusion Medicine, The Ottawa Hospital and Eastern Ontario Regional Laboratory Association, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Elianna
authors.initials: E
authors.lastname: Saidenberg
mesh_terms: D001787:Blood Group Incompatibility / Q000097:blood* / Q000209:etiology*; D001788:Blood Grouping and Crossmatching; D017707:Erythrocyte Transfusion / Q000009:adverse effects*; D005260:Female; D006461:Hemolysis; D006801:Humans; D007518:Isoantibodies / Q000097:blood*; D008508:Medication Errors; D008562:Membrane Glycoproteins / Q000097:blood*; D008666:Metalloendopeptidases / Q000097:blood*; D008875:Middle Aged
chemical_list: D007518:Isoantibodies; D008562:Membrane Glycoproteins; C585978:KEL protein, human; D008666:Metalloendopeptidases
keywords: Acute extravascular hemolysis; Anti-Kpa antibody; Electronic crossmatch