Pre- and posttransfusion indices of hematology, erythropoiesis, and iron physiology. There were 31 patients before transfusion and 26 after transfusion. Following transfusion, mean (A) Hb increased (mean pretransfusion 101.9 g/L [98.1, 105.7], posttransfusion 122.2 g/L [117.0, 127.4], P < .0001; change 20.5 g/L [16.1, 24.8]), (B) EPO decreased (pretransfusion 54.7 mIU/mL [41.3, 72.4], posttransfusion 25.6 mIU/mL [20.0, 32.8], P < .0001, percentage change −49.4% [−58.4, −40.5]), (C) GDF-15 decreased (pretransfusion 7556.2 pg/mL [6016.5, 9490.8], posttransfusion 4979.6 pg/mL [3910.8, 6340.5], P < .0001, percentage change −35.6% [−41.3, −29.9]), (D) sTfR did not significantly vary (pretransfusion 2.95 mg/L [2.43, 3.54], posttransfusion 2.79 mg/L [2.30, 3.35], P = .0937, percentage change −2.0% [-5.3, 1.3]), (E) ferritin increased (pretransfusion 987.7 ng/mL [726.2, 1343.2], posttransfusion 1086.3 ng/mL [806.2, 1463.6], P = .0021, percentage change 18.7% [8.3, 29.1]); (F) CRP did not vary significantly (pretransfusion 1.78 mg/L [1.11, 2.68], posttransfusion 1.88 mg/L [1.06, 3.02], P = .7423, percentage change 22.9% [−8.8, 54.6]); (G) hepcidin increased (pretransfusion 19.2 ng/mL [12.7, 29.8], posttransfusion 41.3 ng/mL [26.3, 64.5], P < .0001, percentage change 154.6% [108.9, 200.2]); and (H) hepcidin-ferritin ratio increased (pretransfusion 0.027 [0.019, 0.036], posttransfusion 0.054 [0.036, 0.072], P = .0001, percentage change 129.7% [75.0, 184.5]). Reticulocyte count (not shown) did not change (pretransfusion 83.6 × 10⁹/L [60.6, 106.6], posttransfusion 80.8 × 10⁹/L [53.4, 108.3], P = .8252).