Clinical predictors of alloimmunization after red blood cell transfusion

BACKGROUND: Development of new red blood cell (RBC) alloantibodies (alloimmunization) is one of the most frequent adverse reactions after an RBC transfusion. Few studies have investigated clinical risk factors for alloimmunization.STUDY DESIGN AND METHODS: In this case‐control study, the characteristics of all patients in whom alloimmunization occurred for the first time after an RBC transfusion in two hospitals between January 1, 2003, and May 5, 2005, were examined and compared to a randomly selected control group who received RBC transfusions in the same hospitals during the same period without alloimmunization. Odds ratios (ORs) for the association between these characteristics and alloimmunization were calculated and analyzed with a logistic regression model.RESULTS: Eighty‐seven cases were found, and 101 controls were selected. Female sex (OR, 1.89; 95% confidence interval [CI], 1.05‐3.38), diabetes mellitus (OR, 2.15; 95% CI, 0.91‐5.05), solid malignancy (OR, 2.07; 95% CI, 1.00‐4.30), and previous allogeneic hematopoietic peripheral blood progenitor cell (PBPC) transplantation (OR, 2.24; 95% CI, 0.64‐7.81) were associated most strongly with alloimmunization, whereas lymphoproliferative disorders (OR, 0.33; 95% CI, 0.13‐0.81) and symptomatic atherosclerosis (OR, 0.52; 95% CI, 0.25‐1.08) were associated with the absence of alloimmunization. All of these associations except for female sex became stronger after adjustment for possible confounders.CONCLUSION: Female sex, diabetes mellitus, solid malignancy, and previous allogeneic PBPC transplantation seem to be risk factors for alloimmunization, whereas lymphoproliferative disorders and symptomatic atherosclerosis seem to protect against it. Further studies are needed to confirm these associations and investigate underlying mechanisms.