A Prospective Study of the Timing and Accuracy of Neutrophil Gelatinase-Associated Lipocalin Levels in Predicting Acute Kidney Injury in High-Risk Cardiac Surgery Patients

Objectives: Neutrophil gelatinase-associated lipocalin (NGAL) appears to be a promising biomarker in the effort to predict acute kidney injury (AKI) after cardiac surgery. The authors aimed to identify the specific time point in the perioperative period at which measurement of either urinary or serum concentrations of NGAL would have the highest predictive power for AKI. The authors also investigated whether change in NGAL from baseline was a better predictor of AKI than absolute NGAL values.

Design: A prospective, investigator-blinded observational study.

Setting: The cardiac surgical unit of a university teaching hospital.

Participants: The study consisted of 50 patients undergoing cardiac surgery who were classified preoperatively as high risk for developing postoperative AKI.

Interventions: No changes to standard practice were required.

Measurements and main results: The authors performed serial measurements of urinary and serum NGAL concentrations at 18 time points throughout the first 48 postoperative hours and assessed the variables required to diagnose AKI with standard criteria. Statistical analysis of predictive ability was performed using the area under receiver operator curves (AUROC) calculated for each time point. It was demonstrated that urinary NGAL performed marginally better than serum NGAL in predicting AKI. Urinary sampling at 4 and 24 hours after initiation of cardiopulmonary bypass provided the greatest diagnostic ability (AUROC, 0.702 and 0.712, respectively). Absolute NGAL values performed better than changes in NGAL values in predicting AKI.

Conclusions: Urinary NGAL performed better than serum NGAL in predicting AKI and was most accurate when measured at 24 hours after initiation of cardiopulmonary bypass; however, NGAL appeared to be at best only a fair predictor of cardiac surgery-associated AKI.