Meta-analysis of randomized controlled trials investigating the risk of postoperative infection in association with white blood cell-containing allogeneic blood transfusion: the effects of the type of transfused red blood cell product and surgical setting.

Previous meta-analyses of the randomized controlled trials (RCTs) investigating the association of perioperative allogeneic blood transfusion (ABT) with postoperative bacterial infection included studies transfusing either autologous or white blood cell (WBC)-reduced allogeneic red blood cells (RBCs) or whole blood to the control arm, and they were unable to investigate the type of RBC product administered as an explanation for the disagreements among the studies. The availability of additional RCTs has permitted investigation of this hypothesis in a meta-analysis restricted to RCTs transfusing WBC-reduced allogeneic RBCs or whole blood to the control arm. In this analysis, across 5 RCTs comparing recipients of non-WBC-reduced versus WBC-reduced allogeneic RBCs, there was no difference (P > .25) in the risk of postoperative infection between recipients of buffy-coat-reduced versus WBC-reduced allogeneic RBCs filtered before storage (summary odds ratio [OR] = 1.19; 95% confidence interval [CI], 0.87-1.63). In contrast, across 3 RCTs, there was an increased (P < .05) risk of postoperative infection in recipients of non-buffy-coat-reduced allogeneic RBCs, or whole blood, as compared with recipients of WBC-reduced allogeneic RBCs, or whole blood, filtered before or after storage (summary OR = 1.77; 95% CI, 1.02-3.09). Moreover, across 3 RCTs that enrolled patients undergoing open-heart surgery, there was an increased (P < .05) risk of postoperative infection in recipients of buffy-coat-reduced (compared with WBC-reduced) allogeneic RBCs (summary OR = 1.39; 95% CI, 1.08-1.80), but the findings of 5 RCTs that enrolled patients having abdominal surgery could not be combined because of extreme variation in the results of the studies. RCTs conducted in the setting of open-heart surgery or transfusing non-buffy-coat-reduced RBCs or whole blood to the treatment arm had administered various RBC products to the control arm, however, and thus the medical heterogeneity of the studies precludes any conclusion about an immunomodulatory (TRIM) effect of ABT mediated by non-buffy-coat-reduced RBC products. To determine whether such a deleterious immunomodulatory effect of ABT exists, additional RCTs transfusing non-buffy-coat-reduced RBCs to the treatment arm should be conducted.