Serum Neutrophil Gelatinase-Associated Lipocalin for Early Detection of Acute Kidney Injury and Outcomes in Critically Ill Patients: A Prospective Study

Background: Early detection of acute kidney injury (AKI), which is common in critical illness, is still difficult to achieve. One possible early biomarker has been identified as Neutrophil gelatinase-associated lipocalin (NGAL).
Objective: In this study, NGAL was measured four hours (NGAL1) and twenty-four hours (NGAL2) after ICU admission in order to predict AKI, renal replacement therapy (RRT), and mortality.
Patients and Methods: Out of the 120 ICU patients enrolled in this prospective observational study, 24 (20%) developed AKI. Serum NGAL levels were measured at 4 and 24 hours. AKI development, RRT requirement, and mortality were monitored in these patients. To ascertain the ideal cut-offs and diagnostic accuracy, ROC analysis was performed.
Results: Patients with AKI had significantly higher NGAL levels. For AKI diagnosis, NGAL1 (cut-off 135 ng/mL) demonstrated 91.7% sensitivity and 99% specificity, while NGAL2 (cut-off 171 ng/mL) slightly outperformed NGAL1 with 95.8% sensitivity and 100% specificity.
 For predicting RRT requirement in patients with AKI, NGAL1 (cut-off 282 ng/mL) and NGAL2 (cut-off 268 ng/mL) both accurately predicted RRT, with 100% sensitivity and 100% specificity.
 Regarding mortality in AKI patients, NGAL1 (cut-off 158 ng/mL) showed 86.7% sensitivity and 77.8% specificity, whereas NGAL2 (cut-off 203 ng/mL) demonstrated 80% sensitivity and 100% specificity, indicating that NGAL2 was a more accurate prognostic indicator.
Conclusion: Serum NGAL is a reliable biomarker for early AKI detection and outcome prediction in critically ill patients. For AKI and mortality, NGAL2 demonstrates marginally better accuracy, but both NGAL1 and NGAL2 perform exceptionally well in predicting RRT. Regular NGAL testing supports tailored care and early intervention.