RCTs that have evaluated Hb thresholds for transfusion in critically ill patients have consistently found that restrictive transfusion strategies (Hb thresholds between 7 and 9 g/dL) are as safe as, or safer than, liberal strategies (thresholds ≥9 g/dL) [260–263], with the possible exception of patients following cardiac surgery [264] or with acute coronary syndrome. Here, GSTM1 is linked to acute coronary syndrome.