Effect of age, sex, and breed on serum cystatin C and creatinine concentrations in dogs.

This study investigated the effects of age, sex and breed on serum cystatin C (Cys-C) and creatinine in small breed dogs. This retrospective study included 250 dogs weighing less than 15 kg without azotemia. Serum Cys-C and creatinine concentrations were analyzed, along with their correlation with age, and the difference between sexes or dog breeds. Serum Cys-C concentration correlated with age (P < 0.001), and did not differ between sexes or dog breeds. By contrast, serum creatinine concentration did not correlate with age. Serum creatinine concentration was higher in males than females (P < 0.05), and was lower in Miniature Dachshunds and Chihuahuas, and was higher in Shiba Inus compared to the general study population (P < 0.001). Serum Cys-C concentration correlates with age, and might be more sensitive to aging-associated subclinical renal dysfunction than serum creatinine concentration in dogs. Unlike serum creatinine concentration, serum Cys-C concentration is not affected by sex or dog breed.