Background and objectives: The diagnosis of acute kidney injury (AKI) is usually based on changes in serum creatinine, which is a poor marker of early renal dysfunction. The discriminative and predictive abilities of serum and urinary cystatin C were examined for the prediction of AKI. Design, setting, participants, & measurements: In this prospective cohort study, serum and urinary cystatin C were serially measured in a heterogeneous group of patients (n = 616) presenting to a tertiary care emergency department. The primary outcome was AKI, classified according to RIFLE and AKIN criteria. The secondary outcome was an adjudication based on clinical criteria to AKI, prerenal azotemia, chronic kidney disease (CKD), and normal kidney function. Results: Patients were adjudicated to have AKI in 21.1%, prerenal azotemia in 25.8%, CKD in 2.4%, and normal kidney function in 50.7%. For the diagnosis of AKI, the discriminatory ability of urinary creatinine and cystatin C was marginal. Both serum cystatin C and serum creatinine (at presentation and 6 hours later) showed high discriminatory ability for the diagnosis of AKI. However, only serum cystatin C attained a significant early predictive power (Hosmer-Lemeshow P value > 0.05). Serum cystatin C could differentiate between AKI and prerenal azotemia, but not between AKI and CKD. Conclusions: Serum cystatin C is an early, predictive biomarker of AKI, which outperforms serum creatinine in the heterogeneous emergency department setting. However, neither biomarker discriminated between AKI and CKD. Additional biomarkers continue to be needed for improved specificity in the diagnosis of community-acquired AKI.

Summary: Background and objectives: The purpose of this study was to determine the accuracy of plasma neutrophil gelatinase-associated lipocalin as a marker of AKI in patients admitted from the emergency department. Design, setting, participants, & measurements: In this prospective cohort study, patients (n=616) admitted from the emergency department from March to November of 2008 were classified according to clinical criteria as AKI, transient azotemia, stable CKD, and normal function. Plasma neutrophil gelatinase-associated lipocalin was measured serially. A logistic regression model using clinical characteristics was fitted to the data, and a second model included discretized plasma neutrophil gelatinase-associated lipocalin. Performance of the models was evaluated by Hosmer–Lemeshow goodness-of-fit test, area under the receiver operating characteristic curve, net reclassification improvement, integrated discrimination improvement, and predictiveness curve. Results: Twenty-one percent of patients were classified as AKI; the highest median levels of plasma neutrophil gelatinase-associated lipocalin were in the AKI group (146–174 ng/ml at various time points) and increased with AKI severity (207–244 ng/ml for Acute Kidney Injury Network classification stage>2). The discriminative ability of plasma neutrophil gelatinase-associated lipocalin for AKI diagnosis (area under the curve, 0.77–0.82 at various time points) improved with higher grades of severity (area under the curve, 0.85–0.89 for AKIN>2). Plasma neutrophil gelatinase-associated lipocalin discriminated AKI from normal function and transient azotemia (area under the curve, 0.85 and 0.73, respectively). Patients were classified into three grades of AKI risk according to plasma neutrophil gelatinase-associated lipocalin levels (low, moderate [i.e., the gray zone], and high). Patients with plasma neutrophil gelatinase-associated lipocalin in the high-risk category displayed a 10-fold greater risk of AKI (odds ratio, 9.8; 95% confidence interval, 5.6 to 16.9). The addition of plasma neutrophil gelatinase-associated lipocalin to the clinical model yielded a net reclassification improvement of 94.3% and an integrated discrimination improvement of 0.122. Conclusion: Plasma neutrophil gelatinase-associated lipocalin is an accurate biomarker for prediction of AKI in patients admitted from the emergency department. This work proposes a three-grade classification of AKI risk based on plasma neutrophil gelatinase-associated lipocalin levels.

Background: Acute Kidney Injury (AKI) is a very frequent complication in the Acute Liver Failure (ALF) population associated with negative outcomes. We aim to evaluate the impact of AKI duration on the outcomes of an ALF population. Methods: A 20-year retrospective analysis of ALF patients admitted to an Intensive Care Unit (ICU) was performed. Chronic liver failure, chronic kidney disease on renal replacement therapy, dialysis requirement within the week prior or an ICU stay of less than 48 h after AKI diagnosis, were exclusion criteria. AKI was defined according to the KDIGO criteria and classified into transient (< 48 h duration) or persistent (48 h duration). Results: A total of 51 patients were included in the analysis and most had AKI (66.7%). Persistent AKI patients (70.6%) presented more frequently with AKI at admission and a higher SOFA score than transient AKI and no AKI, p < 0.05. More severe AKI, sepsis, vasopressor support and mechanical ventilation were also more common (p < 0.05). Nineteen (55.9%) were classified as persistent AKI exclusively by serum creatinine and 15 (44.1%) by both serum creatinine and urine output criteria. Mean survival time at 30 days was 11.3 days for persistent AKI, 25.3 days for transient AKI and 27.0 days for no AKI, p = 0.01. Adjusted multivariate cox regression analysis showed that persistent AKI predicted in-hospital mortality but it lost significance when AKI severity was introduced in the model. Conclusion: Persistent AKI was common in ALF patients and associated with more severe AKI, worst systemic complications and a higher 30-day mortality, compared to transient and no AKI patients.