Value of urine/serum Neutrophil gelatinase-associated lipocalin ratio in distinguishing acute kidney injury from chronic kidney disease.

Objective: This study was performed to test the hypothesis that neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker would be helpful for differentiation acute kidney injury (AKI) from chronic kidney disease (CKD) in kidney malfunction patients from the nephrology department.

Methods: This retrospective study included 355 patients admitted from the nephrology department with modification of diet in renal disease estimated glomerular filtration rate (MDRD eGFR) < 60 ml/min/1.73 m. The subjects were categorized into AKI group (n = 204) and CKD group (n = 151). A propensity-matched analysis, incorporating 17 variables, was performed to control potential selection bias.

Results: Urinary NGAL (uNGAL) level in the AKI group was higher than in the CKD group (372.10 (170.10-690.63) vs 88.10 (52.00-238.80), P < 0.001), but there was no significant difference in serum NGAL (sNGAL). Both sNGAL and uNGAL had a correlation with MDRD eGFR in total patients, AKI patients, and CKD patients. The propensity-matched analysis enrolled 75 patients in each group. In matched AKI group, sNGAL was lower (401.20 (239.10-616.00) vs 468.50 (305.00-709.40), P = 0.049) and uNGAL was elevated (284.00 (136.90-690.90) vs 203.70 (69.20-596.00), P = 0.032), compared with the matched CKD group. In all patients (n = 355), the ratio of uNGAL and sNGAL (u/s NGAL), fractional excretion of NGAL (Fe NGAL) discriminated AKI from CKD (area under the curve, 0.803 and 0.790, respectively). After stratified kidney function, the sub-analyses found that u/s NGAL and Fe NGAL were shown to differ substantially between the AKI group and CKD group (all P < 0.01). The u/s NGAL ratio always had the highest AUC area in the sub-analyses.

Conclusions: u/s NGAL might be helpful to discriminate AKI from CKD in kidney malfunction patients admitted to the nephrology department. Further confirmatory studies might be warranted.