GSTM1 and anemia (phenotype): In a large retrospective study on 1150 TBI patients in which 46 % of patients received RBCT when Hb levels were below 9 g/dl, Salim et al. [26] found that RBCT was associated with an increased hospital mortality in a logistic regression model (adjusted OR 2.19, 95 % CI 1.27–3.75, p = 0.004), while anemia was not.