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

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.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 m2. 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.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.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.