FABP1 and acute kidney injury: By using urinary L-FABP/creatinine ratio, the performance of urinary L-FABP in discriminating postoperative AKI was further improved, with AUROCs of 0.627 (95% CI, 0.533–0.722) at the first timepoint and 0.727 (95% CI, 0.643–0.811) at the second timepoint.