Urine NGAL predicts severity of acute kidney injury after cardiac surgery: a prospective study

Abstract

Background and objectives: The authors have previously shown that urine neutrophil gelatinase-associated lipocalin (NGAL), measured by a research ELISA, is an early predictive biomarker of acute kidney injury (AKI) after cardiopulmonary bypass (CPB). In this study, whether an NGAL immunoassay developed for a standardized clinical platform (ARCHITECT analyzer, Abbott Diagnostics Division, Abbott Laboratories, Abbott Park, IL) can predict AKI after CPB was tested.

Design, setting, participants, & measurements: In a pilot study with 136 urine samples (NGAL range, 0.3 to 815 ng/ml) and 6 calibration standards (NGAL range, 0 to 1000 ng/ml), NGAL measurements by research ELISA and by the ARCHITECT assay were highly correlated (r = 0.99). In a subsequent study, 196 children undergoing CPB were prospectively enrolled and serial urine NGAL measurements obtained by ARCHITECT assay. The primary outcome was AKI, defined as a > or = 50% increase in serum creatinine.

Results: AKI developed in 99 patients (51%), but the diagnosis using serum creatinine was delayed by 2 to 3 d after CPB. In contrast, mean urine NGAL levels increased 15-fold within 2 h and by 25-fold at 4 and 6 h after CPB. For the 2-h urine NGAL measurement, the area under the curve was 0.95, sensitivity was 0.82, and the specificity was 0.90 for prediction of AKI using a cutoff value of 100 ng/ml. The 2-h urine NGAL levels correlated with severity and duration of AKI, length of stay, dialysis requirement, and death.

Conclusions: Accurate measurements of urine NGAL are obtained using the ARCHITECT platform. Urine NGAL is an early predictive biomarker of AKI severity after CPB.

Figure 1.

Correlation between urine NGAL measurements obtained by ARCHITECT® platform and research-based NGAL ELISA assay (AntibodyShop).

Figure 2.

Serum creatinine measurements obtained at various time points post-CPB. AKI, acute kidney injury, defined as a 50% increase in serum creatinine from baseline. Values are mean ± SEM and are shown in Table 2. *P < 0.05 comparing AKI versus no AKI groups.

Figure 3.

Urine NGAL measurements obtained by ARCHITECT® assay at various time points post-CPB. AKI, acute kidney injury, defined as a 50% increase in serum creatinine from baseline. Values are mean ± SEM and are shown in Table 3. *P < 0.05 comparing AKI versus no AKI groups.