Abstract
Feline chronic kidney disease (CKD) has highly variable patterns of progression. Objective methods to differentiate cats with stable and progressive CKD are lacking. This retrospective study aimed to determine a slope cutoff for reciprocal of creatinine (creatinine-1) vs time to objectively differentiate stable and progressive feline CKD, and identify risk factors for CKD progression within 3 months of CKD diagnosis. Euthyroid client-owned cats with azotaemic CKD (n = 321) were included in this study. CKD cats that demonstrated stable (<25% increase) plasma creatinine concentration for >365 days (n = 194) were identified and the reciprocal plot of plasma creatinine vs time (creatinine-1 plot) from these cats was used to determine a cutoff to differentiate stable from progressive CKD. Risk factors for progressive CKD, including response to 3 months of standard treatment, were explored by binary logistic regression. Variables associated with mortality were evaluated using Cox regression. A slope cutoff of -9.5×10-5L/μmol/month (-8.4×10-3dL/mg/month) for creatinine-1 plot distinguished stable (n = 231) vs progressive (n = 90) CKD cats. Baseline plasma log-transformed fibroblast growth factor-23 (ln[FGF-23]), albumin concentrations, advancing age, and slope of creatinine-1, phosphate and body weight within the first 84 days of CKD diagnosis were independent risk factors for progression. Progressive cats had shorter median survival time [95% CI] than non-progressive cats (287 [246-354] vs 894 [812-1052] days; P < 0.001). Overall, cats with stable and progressive CKD can be distinguished using slope of creatinine-1 plot. Risk factors identified may facilitate early detection of cats with progressive CKD.