The ROC curve analysis revealed that lower erythrocyte SOD1 activity was associated with AKI development (AUC 0.686; CI 95 % 0.595–0.777; p < 0.001) at the cutoff of <3.32 U/mg Hb [sensibility: 68.7 % (CI 95 % 57.6–79.8 %); specificity: 55.4 % (CI 95 % 43.3–67.5 %); positive predictive value: 61.3 % (CI 95 % 50.3–72.3 %); negative predictive value: 63.2 % (CI 95 % 50.7–75.7 %)] (Table 3; Fig. 4). The gene discussed is GSTM1; the disease is acute kidney injury.