Serum Clusterin as a Sensitive Biomarker for Kidney Disease in Cats: A Comparative Evaluation in Acute Kidney Injury and Chronic Kidney Disease
Abstract
Current biomarkers for feline kidney disease, including creatinine and blood urea nitrogen (BUN), have limited sensitivity for early injury and do not reliably distinguish acute kidney injury (AKI) from chronic kidney disease (CKD). This study aimed to evaluate serum and urinary clusterin (CLU) levels in felines presenting urinary system disorders, with a focus on acute kidney injury (AKI) and chronic kidney disease (CKD), to determine its potential as a sensitive biomarker of renal pathology. In the study group, blood samples were collected from a total of 38 cats. For the primary analysis, cats were classified according to their predominant renal status into two mutually exclusive groups: chronic kidney disease (CKD, n=19), acute kidney injury (AKI, n=19) from various breeds brought to Erciyes University Training and Research Hospital. Control group samples were also taken from 10 healthy cats brought to the same center for general health control. Clusterin quantification was performed using a competitive enzyme-linked immunosorbent assay (ELISA). Results indicated that mean serum clusterin concentrations were significantly elevated in diseased cats. The mean serum clusterin level was found to be 42.87 μg/mL (34.51 - 57.17) in all sick cats and 36.42 μg/mL (29.08 - 48.39) in healthy cats. Cats with chronic renal failure had statistically significantly higher mean clusterin levels (84.79±61.87 μg/ mL) than cats with acute kidney failure (38.80±15.18 μg/mL) (P<0.001). Correlation analyses revealed strong positive associations between serum clusterin and conventional renal injury markers, including blood urea nitrogen (BUN, r=0.756), creatinine (r=0.829), and phosphorus (r=0.744; all P<0.001). Serum clusterin concentrations differed significantly between cats with renal disease and healthy controls and were further assessed by ROC analysis for discrimination between CKD and AKI. At an optimal cut-off value of 3.11, sensitivity was 77.8%, and specificity was 25%, indicating limited discriminatory performance. Despite statistical differences between groups, substantial overlap and low specificity resulted in poor classification accuracy. Overall, serum clusterin shows an association with renal disease status; however, its ability to distinguish CKD from AKI is limited under the current conditions, and it should not be considered a stand-alone diagnostic marker.