Predictive performance of neutrophil gelatinase-associated lipocalin (NGAL) in acute kidney injury in septic patients

Objective To assess the capability of serum and urine neutrophil gelatinase-associated lipocalin (NGAL) in predicting acute kidney injury (AKI) in septic patients. Methods From July 1, 2014 through December 31, 2014, a prospective observational study of septic patients without AKI was carried out in Renmin Hospital, Tianjin Hospital, and Nankai Hospital, Tianjin. The patients with AKI which was developed after admission to intensive care unit (ICU) were assigned to AKI group and the patients without AKI were assigned to non-AKI group. Clinical data and serum and urine sample were collected at the admission, and at 12, 24, 36, 48, 60, 72 , 84 and 96 hours after admission for detecting creatinine and NGAL. The measurement data accorded with normal distribution were used for t test or variance analysis of repeated measures; comparison of measurement data in non-normal distribution was carried out using the Mann-Whitney U test or Fridman test; comparison of count data was performed using Fisher exact probability method. ROC curve of serum or urine NGAL was plotted and the diagnostic values of serum or urine NGAL in predicting AKI were assessed by calculation of the area under the receiver operating characteristic curve (AuROC). Results Fifty septic patients were included. Thirty-five patients were in AKI group and fifteen in non-AKI group. The median age of AKI group was 73 [interquartile range (IQR), 66-83] and the median age of non-AKI group was 60 (IQR, 47-82). The urine NGAL (uNGAL) concentration in AKI group was higher than that in non-AKI group at the every interval and serum NGAL (sNGAL) was higher in AKI group than that in non-AKI group at only first twointervals. The uNGAL showed the capability of prediction for AKI progression at the 48 hour (AuROC=0.83, 95% CI: 0.70-0.97), 36 hours (AuROC=0.75, 95%CI: 0.59-0.91), 24 hours (AuROC=0.83, 95%CI: 0.70-0.95), 12 hours (AuROC=0.73, 95%CI: 0.60-0.88) prior to AKI occurred. The sNGAL showed capability of prediction at the 48 hours (AuROC=0.69, 95%CI: 0.51-0.88), 36 hours (AuROC=0.69, 95%CI: 0.52-0.87) prior to AKI occurred. Conclusions The sNGAL and uNGAL both were useful biomarker that predicted development of AKI in early stage. But the performance of sNGAL was slightly inferior to that of uNGAL for predicting development of AKI. Key words: Neutrophil gelatinase-associated lipocalin; Acute kidney injury; Sepsis; Receiver operating characteristic curve; Area under receiver operating characteristic curve; Diagnosis; Prognosis