title: Anti-K formation is not associated with the storage time of transfused red blood cells.
abstract: BACKGROUND
  The formation of red blood cell (RBC) antibodies could be enhanced by the presence of inflammation caused by prolonged RBC storage, as was shown in animal studies. The low occurrence (<10%) of K-antigen in most populations often enables identification of the K+ RBC unit that triggered anti-K formation and determination of its storage time. This study aims to quantify the association of anti-K formation with RBC storage time.
  
  
  METHODS
  K- patients who had not been previously transfused and received at least 1 K+ unit between January 2004 and August 2013 were identified. First, the influence of storage time of the K+ units was assessed as mean, maximum, and minimum storage times within one transfusion interval and at various cutoff points for old versus young blood (14, 18, and 21 days). Second, concomitantly transfused K- units were studied within different periods surrounding the K+ unit(s).
  
  
  RESULTS
  Twenty-three patients formed anti-K, while 274 patients did not. The adjusted relative risks of anti-K formation for mean, maximum, and minimum storage time (days) ranged from 1.01 to 1.03 (95% confidence interval, 0.96-1.08). When analyzing the association between only "younger" and only "older" K+ units at various cutoff points, no association was found. Similarly, no association was found between storage time of the concomitantly transfused K- units and anti-K formation.
  
  
  CONCLUSIONS
  Within the range of storage times used in normal clinical practice in the Netherlands, no association could be found between RBC storage time and anti-K formation.
authors.affiliation: Center for Clinical Transfusion Research, Sanquin Research, Leiden, the Netherlands.
authors.forename: Esther
authors.initials: E
authors.lastname: Hogervorst
authors.affiliation: Center for Clinical Transfusion Research, Sanquin Research, Leiden, the Netherlands.|Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Rutger
authors.identifier: http://orcid.org/0000-0002-6545-7277
authors.initials: R
authors.lastname: Middelburg
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Anneke
authors.initials: A
authors.lastname: Brand
authors.affiliation: Center for Clinical Transfusion Research, Sanquin Research, Leiden, the Netherlands.
authors.forename: Leo
authors.initials: L
authors.lastname: van de Watering
authors.affiliation: Center for Clinical Transfusion Research, Sanquin Research, Leiden, the Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Schonewille
mesh_terms: D000367:Age Factors; D000368:Aged; D000942:Antigens, Bacterial / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D001787:Blood Group Incompatibility / Q000453:epidemiology / Q000209:etiology / Q000276:immunology; D001793:Blood Preservation / Q000009:adverse effects / Q000379:methods; D017707:Erythrocyte Transfusion / Q000009:adverse effects*; D004912:Erythrocytes / Q000276:immunology; D005260:Female; D005500:Follow-Up Studies; D006650:Histocompatibility Testing / Q000379:methods; D006801:Humans; D007518:Isoantibodies / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D007518:Isoantibodies; C030659:K antigens