Neutrophil Gelatinase-associated Lipocalin in Critically ill Septic Children With and Without Acute Kidney Injury

Neutrophil gelatinase-associated lipocalin (NGAL) is a rapidly emerging biomarker for early detection of acute kidney injury (AKI). The aim of the study is to evaluate the impact of sepsis on serum NGAL in critically ill children, and to investigate whether the presence of sepsis affects the ability of serum NGAL to predict AKI. Thirty-five patients, who met criteria of sepsis and related syndromes, were classified into three groups (septic shock, systemic inflammatory response syndrome (SIRS), and severe sepsis). They were reclassified regarding who developed AKI into AKI and non- AKI groups. Thirty-two sex and age matched healthy subjects served as a control group. Serum NGAL was assayed using Enzyme-linked Immunosorbent Assay (ELISA), and serum creatinine was measured using kinetic spectrophotometric method. Serum NGAL levels were significantly high in critically ill septic patients compared to healthy controls (median: 51.1ng/ml vs. 8 ng/ml, P=0.001), and were significantly higher in septic shock (median 87ng/ml) than in SIRS (median 37ng/ml) or in severe sepsis (median 42ng/ml) with P values of 0.01 and 0.02, respectively. However, there was no significant difference in the levels of serum NGAL between AKI patients and non- AKI patients (P=0.16). Receiver operating characteristic (ROC) curve analysis of serum NGAL for prediction of AKI showed an area under the curve (AUC) =0.65, cutoff value (C.O.) = 47ng/ml, sensitivity= 84.6%, specificity=52.6%, positive predictive value (PPV) =55%, negative predictive value (NPV) =83.3%, and accuracy = 66% vs. AUC of 0.95, C.O. of 0.45 mg/dl, sensitivity= 92.3%, specificity 73.7%, PPV=70.6%, NPV=93.3% and accuracy=81% for serum creatinine. In conclusion, serum NGAL is raised in critically ill septic children in pediatric ICU and is a marker of bacterial infection and systemic inflammation. However, in AKI associated with sepsis, serum NGAL is not a specific biomarker for the prediction of AKI and it loses its early predictive property. In such patients, serum creatinine is more specific than serum NGAL.