Biomarkers for acute kidney injury in critically ill patients.

Acute kidney injury (AKI) is a common and frequently fatal illness in critically ill patients, with a high associated-mortality. Early recognition of kidney injury and prompt corrective measures may improve outcome. Finding an early, accurate and reproducible biomarker for AKI is a research priority. In recent years, many urinary or plasma proteins have been investigated, some of them promising, but the ideal biomarker remains to be discovered. Cystatin C, neutrophil gelatinase-associated lipocalin, interleukin-18, fatty acid-binding proteins and kidney injury molecule 1 seem to be more accurate markers for AKI as compared with the traditional serum creatinine. However, their ability to predict worsening of AKI and need for renal replacement therapy (RRT) is not clear, and current available data are insufficient to recommend the use of these biomarkers routinely for clinical decision-making. Thus, using a combination of different urinary and plasma biomarkers and clinical observations, such as oliguria, may modify the clinical variability for therapeutic interventions, such as RRT initiation, and improve outcome. The purpose of this review was to summarize recent findings concerning biomarkers for AKI, especially in the intensive care unit setting, to highlight their strengths and weaknesses, and to determine their usefulness in clinical practice.