Neutrophil Gelatinase-Associated Lipocalin Curve and Neutrophil Gelatinase-Associated Lipocalin Extended-Range Assay: A New Biomarker Approach in the Early Diagnosis of Acute Kidney Injury and Cardio-Renal Syndrome

Cardio-Renal syndrome (CRS) is a common and complex clinical condition in which multiple causative factors are involved. The time window between renal insult and development of acute kidney injury (AKI) in acute heart failure (AHF) can be varied in different patients and AKI often is diagnosed too late, only when the effects of the insult become evident with a loss or decline of renal function. For this reason, pharmaceutical interventions for AKI that have been shown to be renoprotective or beneficial when tested in experimental conditions do not display similar results in the clinical setting. In most cases patients with AHF are admitted with clinical signs and symptoms of congestion and fluid overload. Loop diuretics, typically used to induce an enhanced diuresis in these congested patients, often are associated with a subsequent significant decrease in glomerular filtration rate and cause a creatinine increase that is apparent within 72 hours. Early detection of AKI is not possible with the use of serum creatinine and there is a need for a timely diagnostic tool able to address renal damage while it is happening. We need to define the diagnosis of both AHF and AKI in the early phases of CRS type 1 by coupling a kidney damage marker such as neutrophil gelatinase-associated lipocalin (NGAL) with B-type natriuretic peptide (BNP). Indeed, it would be ideal to make available a panel including whole blood or plasma cardiac and renal biomarkers building specific, pathophysiologically based, molecular profiles. Based on current knowledge and consensus, we can use kidney damage biomarkers such as plasma NGAL for an early diagnosis of AKI. However, differences in individual patient values and uncertainties about the ideal cut-off values may currently limit the application of these biomarkers. We propose that NGAL may increase its usefulness in the diagnosis and prevention of CRS if a curve of plasma values rather than a single plasma measurement is determined. To apply the concept of measuring an NGAL curve in AHF patients, however, assay performance in the lower-range values becomes a critical factor. For this reason, we propose the use of the new extended-range plasma NGAL assay that may contribute to remarkably improve the sensitivity of AKI diagnosis in AHF and lead to more effective intervention strategies. Semin Nephrol 32:121-128 (C) 2012 Elsevier Inc. All rights reserved.