Effect of age of red cells for transfusion on patient outcomes: a systematic review and meta-analysis

Longer storage duration of red blood cell (RBC) units prior to transfusion has been associated with worse outcomes in observational studies. We performed a systematic review, including recently published randomized trials, to determine if storage age of RBCs is associated with mortality, morbidity or adverse events in patients. Searches were performed up to 21st July 2017 in Medline (OvidSP), 20 July in EMBASE (OvidSP) and June 2017 in Cochrane Library. Eligible studies were randomized controlled trials comparing transfusion of fresher or freshest available with older or standard issue RBCs. Human volunteer and autologous RBC transfusion studies were excluded. Data were extracted from published reports independently by 2 authors and strength of evidence assessed according to GRADE criteria. The primary outcome was latest-reported mortality. Sixteen trials randomizing 31,359 patients were identified. Transfusion with fresher compared with older RBC was not associated with risk of death (relative risk [RR] 1.04, 95% CI 0.98-1.09; P = .20, I2 = 0%, high quality evidence), but was associated with higher risk of transfusion reactions (RR 1.35, 95% CI 1.04-1.76; P = .02; I2 = 0%; high quality evidence) and infection (RR 1.08, 95% CI 1.00-1.17; P = .05; I2 = 0%, moderate evidence). Trial sequential analysis showed required information size has now been reached to exclude a 10% relative risk increase or decrease in mortality. Transfusion of fresher RBCs is not associated with decreased risk of death but is associated with higher rates of transfusion reactions and possibly infection. The current evidence does not support a change from current usual transfusion practice.