title: Exposure to ABO-nonidentical blood associated with increased in-hospital mortality in patients with group A blood.
abstract: BACKGROUND
  Transfusing ABO-compatible blood avoids most acute hemolytic reactions, but donor units that are ABO compatible are not necessarily ABO identical. Emerging data have raised concerns that ABO-nonidentical blood products lead to adverse outcomes.
  
  
  METHODS
  A large multihospital registry (Transfusion Registry for Utilization, Surveillance, and Tracking) was used to determine the association between exposure to ABO-nonidentical blood and in-hospital mortality. Cox regression analyses controlled for sex, age, hemoglobin, creatinine, and in-hospital interventions and stratified by age of blood and admission year.
  
  
  RESULTS
  Data from 18,843 non-group O patients admitted between 2002 and 2011 and receiving at least 1 unit of blood were analyzed. Overall, group A patients had significantly increased risk of in-hospital death upon receiving a nonidentical unit (RR , 1.79; 95% CI, 1.20-2.67; p = 0.005). There was no evidence of increased risk for group B or AB patients. Similar results were seen when only patients with circulatory disorders were considered. When patients with an injury or poisoning diagnosis were excluded, the risk of in-hospital death after receiving a non-identical unit was significantly higher in group A patients and significantly lower in Group B patients.
  
  
  CONCLUSIONS
  Our study demonstrates an adverse effect of ABO-nonidentical blood in a broad range of patients with group A blood, after adjustment for potential confounders. Further research in this area is required to study possible mechanisms. Increased mortality associated with exposure to nonidentical blood in these patients would have a substantial impact at the population level; it would challenge how blood suppliers manage inventory and recruit donors and how health care providers administer blood.
authors.affiliation: Transfusion Research Program.|Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Menaka
authors.initials: M
authors.lastname: Pai
authors.affiliation: Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Cook
authors.affiliation: Transfusion Research Program.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Barty
authors.affiliation: Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Eikelboom
authors.affiliation: Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Ker-Ai
authors.initials: KA
authors.lastname: Lee
authors.affiliation: Transfusion Research Program.|Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Nancy
authors.initials: N
authors.lastname: Heddle
mesh_terms: D000017:ABO Blood-Group System / Q000502:physiology*; D000368:Aged; D000369:Aged, 80 and over; D001787:Blood Group Incompatibility / Q000503:physiopathology*; D001788:Blood Grouping and Crossmatching; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D065227:Transfusion Reaction
chemical_list: D000017:ABO Blood-Group System