Urinary neutrophil gelatinase-associated lipocalin in dogs with stable or progressive kidney disease

Background: Active kidney injury may play a role in chronic kidney disease (CKD) progression in dogs. Neutrophil gelatinase-associated lipocalin (NGAL), a novel tubular kidney injury biomarker, may help differentiate progressive CKD from stable CKD in dogs. Objectives: To determine if urinary NGAL : creatinine ratio (UNCR) differentiates stable and progressive CKD in dogs. We hypothesized that UNCR would be higher in dogs with progressive CKD versus stable CKD. Animals: Twenty-one healthy control dogs, 22 with prerenal azotemia, 19 with stable CKD, 30 with progressive CKD, and 27 with acute kidney injury (AKI). Methods: Prospective study. Azotemic (serum creatinine concentration >1.6 mg/dL) dogs or nonazotemic AKI dogs were enrolled and classified into 4 groups: (1) prerenal azotemia, (2) stable CKD, (3) progressive CKD, and (4) AKI. Urinary NGAL was measured by ELISA and UNCR compared among groups. Urine protein : creatinine ratio (UPC) in dogs with stable and progressive CKD was compared to UNCR for differentiating CKD groups. Results: UNCR was significantly higher in dogs with progressive CKD than stable CKD. UNCR of the prerenal azotemia group was significantly lower than that of the progressive CKD and AKI groups. No significant difference was found in UNCR between stable CKD and prerenal azotemia groups. ROC curve analysis of UNCR for differentiating progressive CKD from stable CKD resulted in an AUC of 0.816 (95% confidence interval [CI], 0.673-0.959), greater than that of UPC (0.696; 95% CI, 0.529-0.863). Conclusions and Clinical Importance: Urinary NGAL could be helpful to predict the risk of progression in dogs with CKD.