Plasma NGAL for the Diagnosis of AKI in Patients Admitted from the Emergency Department Setting

Abstract

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. 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. 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. 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.