Associations between change from pre- to posttransfusion. Associations between indices that changed significantly from pre- to posttransfusion were evaluated (ie, Hb, ferritin, EPO, GDF-15, and hepcidin). (A) Transfused volume of red cells normalized for patient blood volume was positively associated with posttransfusion change in Hb (r = 0.56, P = .0033). (B) Posttransfusion change in Hb was inversely associated with change in EPO (r = −0.56, P = .0034) and positively with change in hepcidin (r = 0.44, P = .0300). (C) Percentage change in EPO was inversely associated with change in hepcidin (r = −0.41, P = .0489). Changes in GDF-15 and sTfR were not associated with change in hepcidin, nor was change in ferritin associated with change in hepcidin (not shown).