Neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker for acute renal injury after cardiac surgery

Background The scarcity of early biomarkers for acute renal failure has hindered our ability to launch preventive and therapeutic measures for this disorder in a timely manner. We tested the hypothesis that neutrophil gelatinase-associated lipocalin (NGAL) is an early biomarker for ischaemic renal injury after cardiopulmonary bypass. Methods We studied 71 children undergoing cardiopulmonary bypass. Serial urine and blood samples were analysed by western blots and ELISA for NGAL expression. The primary outcome measure was acute renal injury, defined as a 50% increase in serum creatinine from baseline. Findings 20 children (28%) developed acute renal injury, but diagnosis with serum creatinine was only possible 1–3 days after cardiopulmonary bypass. By contrast, urine concentrations of NGAL rose from a mean of 1·6 μg/L (SE 0·3) at baseline to 147 μg/L (23) 2 h after cardiopulmonary bypass, and the amount in serum increased from a mean of 3·2 μg/L (SE 0·5) at baseline to 61 μg/L (10) 2 h after the procedure. Univariate analysis showed a significant correlation between acute renal injury and the following: urine and serum concentrations of NGAL at 2 h, and cardiopulmonary bypass time. By multivariate analysis, the amount of NGAL in urine at 2 h after cardiopulmonary bypass was the most powerful independent predictor of acute renal injury. For concentration in urine of NGAL at 2 h, the area under the receiver-operating characteristic curve was 0·998, sensitivity was 1·00, and specificity was 0·98 for a cutoff value of 50 μg/L. Interpretation Concentrations in urine and serum of NGAL represent sensitive, specific, and highly predictive early biomarkers for acute renal injury after cardiac surgery.