Using lipocalin as a prognostic biomarker in acute kidney injury

Introduction: Human lipocalin-2, known as neutrophil gelatinase-associated lipocalin (NGAL), is a widely studied biomarker of acute kidney injury (AKI).Areas covered: NGAL can serve as a predictor of AKI, disease progression, and mortality and can help in differentiating between AKI etiologies. We conducted a systematic review in the PubMed and Medline databases involving the clinical application of NGAL in patients with AKI.Expert opinion: In this review, we explored the usefulness of NGAL for AKI or clinical outcome prediction. The use of urine or blood NGAL levels alone or in combination with a clinical prediction model may facilitate AKI prediction, severity prediction, AKI etiological differentiation, and mortality prediction. For AKI prediction, urine and plasma NGAL levels have an area under the curve (AUC) ranging from 0.71 to 0.90 and from 0.71 to 0.89, respectively, in different populations. The diagnostic performance of NGAL alone for renal replacement therapy or successful discontinuation prediction is suboptimal (AUC range: 0.65-0.81). Sepsis limits the application of NGAL as a clinical predictor, and the prediction performance of NGAL is affected by baseline renal function, timing of sample collection, and underlying comorbidities. The lack of internationally approved reference material also limits the usefulness of NGAL.