Preliminary evaluation of a particle-enhanced turbidimetric immunoassay (PETIA) for the determination of serum cystatin C-like immunoreactivity in dogs.

Serum cystatin C often is used in humans as a rapid and more sensitive marker than serum creatinine for glomerular filtration rate. The purpose of the present study was to evaluate whether cystatin C-like immunoreactivity (CLI) could be measured reliably in canine serum and to investigate whether dogs with clinical renal insufficiency had higher CLI levels than did clinically healthy dogs and dogs with nonrenal diseases. A commercially available particle-enhanced turbidimetric immunoassay (PETIA) for human serum cystatin C was used to measure canine serum CLI in a linear and proportional manner, with a mean recovery of 104% +/- 7.5% and coefficients of variation of 1.7 to 9.6%. The assay was then applied to serum samples from 17 clinically healthy dogs, 12 dogs with nonrenal diseases, and 8 dogs with renal insufficiency. Serum CLI was significantly higher in dogs with renal insufficiency (median serum CLI = 5.01 mg/L) than in clinically healthy dogs and dogs with nonrenal diseases (median serum CLI = 1.06 mg/L and 1.62 mg/L, respectively). Thus, canine serum CLI could be reliably measured using a commercially available PETIA designed for human serum cystatin C, and dogs with clinical renal insufficiency had, as expected, significantly higher serum CLI levels.