Different molecular forms of urinary neutrophil gelatinase-associated lipocalin (NGAL) have recently been discovered. We aimed to explore the nature, source and discriminatory value of urinary NGAL in intensive care unit (ICU) patients. Methods: We simultaneously measured plasma NGAL (pNGAL), urinary NGAL (uNGAL), and estimated monomeric and homodimeric uNGAL contribution using Western blotting-validated enzyme-linked immunosorbent assays [uNGALE1 and uNGALE2] and their calculated ratio in 102 patients with the systemic inflammatory response syndrome and oliguria, and/or a creatinine rise of >25 ?mol/L. Measurements and main results: Bland-Altman analysis demonstrated that, despite correlating well (r = 0.988), uNGAL and uNGALE1 were clinically distinct, lacking both accuracy and precision (bias: 266.23; 95 CI 82.03-450.44 ng/mg creatinine; limits of agreement: -1,573.86 to 2,106.32 ng/mg creatinine). At best, urinary forms of NGAL are fair (area under the receiver operating characteristic [AUROC] =0.799) predictors of renal or patient outcome; most perform significantly worse. The 44 patients with a primarily monomeric source of uNGAL had higher pNGAL (118.5 ng/ml vs. 72.5 ng/ml; p <0.001), remaining significant following Bonferroni correction. Conclusions: uNGAL is not a useful predictor of outcome in this ICU population. uNGAL patterns may predict distinct clinical phenotypes. The nature and source of uNGAL are complex and challenge the utility of NGAL as a uniform biomarker.
- Apache Acute Kidney Injury/*diagnosis/etiology/urine Acute-Phase Proteins/*urine Aged Area Under Curve Biomarkers/blood/urine Blotting, Western Creatinine/blood *Critical Illness Female Humans Intensive Care Units/statistics & numerical data Lipocalins/blood/*urine Male Middle Aged Oliguria/complications/diagnosis/etiology Predictive Value of Tests Prospective Studies Risk Assessment/methods Systemic Inflammatory Response Syndrome/*complications/diagnosis Victoria
Glassford, N. J., Schneider, A., Xu, S., Eastwood, G. M., Young, H., Peck, L., Venge, P., & Bellomo, R. (2013). The nature and discriminatory value of urinary neutrophil gelatinase-associated lipocalin in critically ill patients at risk of acute kidney injury. Intensive Care Medicine, 39(10), 1714-1724. https://doi.org/10.1007/s00134-013-3040-7