Urinary Biomarkers in the Early Detection of Acute Kidney Injury after Cardiac Surgery

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Abstract
Background and objectives: Serum creatinine (Scr) does not allow for early diagnosis of acute kidney injury (AKI). The diagnostic utility of urinary kidney injury molecule-1 (KIM-1), N-acetyl-β-D-glucosaminidase (NAG), and neutrophil gelatinase associated lipocalin (NGAL) was evaluated for the early detection of postoperative AKI in a prospective study of 90 adults undergoing cardiac surgery. Designs, setting, participants, & measurements: Urinary KIM-1, NAG, and NGAL were measured at 5 time points for the first 24 h after operation and normalized to the urinary creatinine concentration after cardiac surgery. Receiver-operating characteristic curves were generated and the areas under the curve (AUCs) compared for performance of biomarkers in detection of postoperative AKI. Results: Thirty-six patients developed AKI, defined as an increase in Scr of ≥0.3 mg/dl within 72 h after surgery. The AUCs for KIM-1 to predict AKI immediately and 3 h after operation were 0.68 and 0.65; 0.61 and 0.63 for NAG; and 0.59 and 0.65 for NGAL, respectively. Combining the three biomarkers enhanced the sensitivity of early detection of postoperative AKI compared with individual biomarkers: the AUCs for the three biomarkers combined were 0.75 and 0.78. The performance of combining biomarkers was even better among 16 early postoperative AKI patients with AUCs of 0.80 and 0.84, respectively. Conclusions: The results of this study support that a combination of urinary biomarkers may allow for early detection of postoperative AKI after cardiac surgery before a rise in Scr.