Analytical validation of a human particle-enhanced nephelometric assay for cystatin C measurement in feline serum and urine

• Published in: Veterinary clinical pathology 2014-06, Vol.43 (2), p.226-234
• Main Authors: Ghys, Liesbeth F. E., Meyer, Evelyne, Paepe, Dominique, Delanghe, Joris, Daminet, Sylvie
• Format: Article
• Language: English
• Subjects: Animals; Antibodies - immunology; Biomarker; Biomarkers - blood; Biomarkers - urine; cat; Cat Diseases - blood; Cat Diseases - diagnosis; Cats; chronic kidney disease; Creatinine - blood; Cystatin C - blood; Cystatin C - urine; Female; Glomerular Filtration Rate - veterinary; Humans; immunoassay; Immunoassay - methods; Immunoassay - veterinary; Male; Nephelometry and Turbidimetry - methods; Nephelometry and Turbidimetry - veterinary; Pilot Projects; Rabbits; Renal Insufficiency, Chronic - blood; Renal Insufficiency, Chronic - diagnosis; Renal Insufficiency, Chronic - veterinary; Reproducibility of Results; Western blot analysis
• ISSN: 0275-6382; 1939-165X
• DOI: 10.1111/vcp.12144

Background In people and dogs, Cystatin C (CysC), a renal glomerular and tubular marker, seems superior to serum creatinine to estimate the glomerular filtration rate (GFR). A particle‐enhanced nephelometric immunoassay is available to measure human CysC, but there are no reports in cats. Objective The goal of this study was the validation of the human CysC nephelometric assay with feline serum and urine, and to perform a pilot study comparing serum and urine CysC between healthy cats and cats with chronic kidney disease (CKD). Methods Western blot analysis was used to assess cross‐reactivity between the polyclonal rabbit anti‐human CysC antibody and feline CysC. Imprecision and linearity were determined for feline serum and urine CysC. Serum and urine CysC were measured in 10 healthy and 10 CKD cats. Results Cross‐reactivity between the polyclonal rabbit anti‐human CysC antibody and feline CysC was demonstrated. Intra‐ and inter‐assay coefficients of variation in feline serum and urine were 1.3% and 0.4%, and 12.5%, and 4.1%, respectively. Cats with CKD had a significantly higher serum CysC concentration (1.24 [0.63–2.99] vs 0.79 [0.43–1.05] mg/L; P = .02) and urine CysC/urinary Creatinine (uCr) ratio (565.6 [0–1311] vs < 0.049/uCr mg/mol; P = .005) compared with healthy cats. Conclusions The human nephelometric assay showed satisfactory validation results for feline CysC. Cats with CKD had a significantly higher sCysC concentration and uCysC/uCr ratio compared with healthy cats. Additional studies are necessary to evaluate CysC as an early marker of renal damage in cats.