Published in:
01-10-2013 | Seven-Day Profile Publication
The nature and discriminatory value of urinary neutrophil gelatinase-associated lipocalin in critically ill patients at risk of acute kidney injury
Published in: Intensive Care Medicine | Issue 10/2013
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Background
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 μmol/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.