ALB and acute kidney injury: The cutoff value of preoperative serum albumin for postoperative AKI occurrence was 37.5 g/L determined by the Youden index (P < 0.001, area under the curve [AUC] = 0.624) with a sensitivity of 0.54, specificity of 0.67, and positive predictive value of 0.36 [see Additional file 3: Figure S1].