Diagnosis of AKI is based on elevation of creatinine or the presence of oliguria.
Serum creatinine is a biomarker of little value because it is influenced by several extra-renal factors.
Advanced renal tissue damage is required to demonstrate AKI and this increasn occurs after 48 h of the injury.
Biomarkers are tools frequently used in the ICU for diagnosis, monitoring and decision making.
Neutrophil Gelatinase-Associated Lipocalin (NGAL) one of the most studied and promising biomarkers for early diagnosis of AKI.
There is increasing evidence that NGAL is not only a marker of AKI but also a predictive factor for severity, mortality and hospital stay and also useful to determine time to initiate renal replacement therapy.
Studies in critically ill patients with AKI showed a 10-fold increase above the reference range of the NAGL in plasma and up to 100 times in urine. Both were correlated with serum creatinine levels. Kidney biopsies showed an accumulation of NAGL immunoreactivity in 50% of the cortical tubules.
NAGL measurement is useful for a large variety of clinical situations that lead to AKI (cardiac surgery, renal transplantation, contrast nephropathy, hemolytic uremic syndrome and hospitalization in the intensive care unit) or chronic kidney injury (lupus nephritis, glomerulonephritis, obstruction, dysplasia, polycystic kidney disease).
NAGL has also been evaluated as a biomarker of AKI in renal transplantation. Kidney biopsies obtained 1 h after vascular anastomosis revealed a significant correlation between NAGL and staining intensity and the subsequent development of early graft function.(1)
Recently published studies suggest that NAGL concentrations in plasma and urine represent a predictive biomarker for AKI in ICUs, being able to predict this complication about 2 days before the increase in serum creatinine concentrations.
Therefore, NAGL is an early marker for renal injury, even in a heterogeneous group of patients with an indeterminate time of the injury.2
(1)Devarajan P. Neutrophil gelatinase-associated lipocalin (NGAL): a new marker of kidney disease. Scand J Clin Lab Invest Suppl 2008;241:89–94.
(2) Zappitelli M, Washburn K, Arikan A, Loftis L, Qing M, Devarajan P. Urine neutrophil gelatinase-associated lipocalin is an early marker of acute kidney injury in critically ill children: a prospective cohort study. Crit Care 2007;11:1-11
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