Serum levels of inflammatory markers do not increase after transfusions of older RBCs compared with fresh RBCs in healthy volunteers. (A) The mean ± SEM for serum IL-6 levels, (B) CRP levels, and (C) individual levels of CRP from before transfusion to 72 hours after transfusion of fresh and older RBCs. Vertical arrows indicate pretransfusion time points; and dotted lines, the reference range. The P values are as specified in the figure comparing the paired area under the curve of the mean of the outcome parameter for the N = 14 volunteers (for IL-6) and N = 12 (for CRP; the first 2 volunteers were not tested because of inadequate sample volume) from 0 to 24 hours after the fresh and older RBC transfusions.