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Kidney biomarkers appear to be useful in differential diagnosis between acute tubular necrosis (ATN) and other types of acute kidney injury (AKI) in cirrhosis, particularly hepatorenal syndrome (HRS-AKI). Distinction is important because treatment is different. However, kidney biomarkers are still not used in clinical practice. The aim of the current study was to investigate the accuracy of several biomarkers in differential diagnosis of AKI and in predicting kidney outcome and patient survival. This was a prospective study of 320 consecutive cases of AKI in patients hospitalized for decompensated cirrhosis. Evaluation of AKI was made with a diagnostic algorithm that included identification and removal/treatment of precipitating factors and albumin administration (1 g/kg for 2 days) to patients with AKI stage 1B or greater. Urinary neutrophil gelatinase-associated lipocalin (NGAL), monomeric NGAL (mNGAL), interleukin-18, and standard biomarkers were measured at diagnosis and on days 3, 7, and 14. Of the 320 cases, 153 were hypovolemia-induced AKI (48%), 93 were HRS-AKI (29%), 39 were ATN (12%), and 35 were due to miscellaneous causes (11%). Among all biomarkers, urinary NGAL measured at day 3 had the greatest accuracy for differential diagnosis between ATN and other types of AKI (area under the receiver operating characteristic curve, 0.87; 95% confidence interval, 0.78-0.95). The cutoff with the best predictive accuracy for ATN diagnosis was 220 µg/g creatinine. Progression of AKI during hospitalization was associated with persistently high NGAL levels, and NGAL was an independent predictive factor of AKI progression. Likewise, NGAL was also an independent predictive factor of 28-day mortality together with Model for End-Stage Liver Disease score. Conclusion: These results support the use of NGAL in clinical practice within the context of a diagnostic algorithm for differential diagnosis of AKI and outcome prediction in cirrhosis., (© 2019 by the American Association for the Study of Liver Diseases.)

Background & Aims Acute-on-chronic liver failure (ACLF) is a syndrome that occurs in cirrhosis characterized by organ failure(s) and high mortality rate. There are no biomarkers of ACLF. The LCN2 gene and its product, neutrophil gelatinase-associated lipocalin (NGAL), are upregulated in experimental models of liver injury and cultured hepatocytes as a result of injury by toxins or proinflammatory cytokines, particularly Interleukin-6. The aim of this study was to investigate whether NGAL could be a biomarker of ACLF and whether LCN2 gene may be upregulated in the liver in ACLF. Methods We analyzed urine and plasma NGAL levels in 716 patients hospitalized for complications of cirrhosis, 148 with ACLF. LCN2 expression was assessed in liver biopsies from 29 additional patients with decompensated cirrhosis with and without ACLF. Results Urine NGAL was markedly increased in ACLF vs. no ACLF patients (108(35–400) vs. 29(12–73) μg/g creatinine; p <0.001) and was an independent predictive factor of ACLF; the independent association persisted after adjustment for kidney function or exclusion of variables present in ACLF definition. Urine NGAL was also an independent predictive factor of 28 day transplant-free mortality together with MELD score and leukocyte count (AUROC 0.88(0.83–0.92)). Urine NGAL improved significantly the accuracy of MELD in predicting prognosis. The LCN2 gene was markedly upregulated in the liver of patients with ACLF. Gene expression correlated directly with serum bilirubin and INR (r = 0.79; p <0.001 and r = 0.67; p <0.001), MELD (r = 0.68; p <0.001) and Interleukin-6 (r = 0.65; p <0.001). Conclusions NGAL is a biomarker of ACLF and prognosis and correlates with liver failure and systemic inflammation. There is remarkable overexpression of LCN2 gene in the liver in ACLF syndrome. Lay summary Urine NGAL is a biomarker of acute-on-chronic liver failure (ACLF). NGAL is a protein that may be expressed in several tissues in response to injury. The protein is filtered by the kidneys due to its small size and can be measured in the urine. Ariza, Graupera and colleagues found in a series of 716 patients with cirrhosis that urine NGAL was markedly increased in patients with ACLF and correlated with prognosis. Moreover, gene coding NGAL was markedly overexpressed in the liver tissue in ACLF. [ABSTRACT FROM AUTHOR]