GSTM1 and chronic kidney disease: For the general population without CKD, patients must have a recorded Hb level ≤ 10 g/dL (≤ 11 g/dL for pregnant women) and be in need of rapid iron replacement and unresponsiveness to or intolerance of oral iron replacement therapy with serum ferritin < 30 ng/mL or TSAT < 20% and occur preoperatively or immediately preceding labor.