In the case of paediatric transfusion, WHO recommends a standard volume for transfusion (20 mls/kg of whole blood or 10 mls/kg of packed cells) for all children with profound (Hb < 4/g/dl) or severe and complicated (Hb < 6/g/dl plus one or more severity features) anaemia, but gives no guidelines for RCCs. This evidence concerns the gene GSTM1 and anemia.