Effect of storage of red blood cells on alloimmunization.

BACKGROUND Red blood cells (RBCs) undergo changes during storage. Various studies have suggested a higher risk of adverse and often multifactorial clinical outcomes associated with older-stored RBCs. Our aim therefore was to examine if storage of transfused RBCs is also associated with the risk of RBC-specific alloantibody formation. STUDY DESIGN AND METHODS A two-center retrospective case-referent study was performed where case patients and control subjects were sampled from all consecutive patients who had received their first and subsequent RBC transfusions in one of the two centers only. Cases were defined as patients who developed a first RBC alloantibody. Control subjects were patients without detectable RBC alloantibodies, who were matched to the case patients regarding number of RBC transfusions. Binary logistic regression analysis was used to examine the association between storage time of RBCS and the occurrence of alloimmunization. RESULTS A total of 144 cases and 286 controls were selected for our study, who had received a total 5478 RBC units. Comparing patients receiving units stored shorter than a certain number of days versus older units (with various storage periods up to 4 weeks) did not reveal an association or a trend between alloimmunization risk and storage time categories. CONCLUSION Our findings suggest that storage times of transfused RBCs between 1 and 4 weeks do not affect the risk of alloimmunization.