Exocell Rat Cystatin C ELISA uses recombinant rat cystatin C (Gly21-Ala140) as standard and a polyclonal antibody raised against recombinant cystatin C. This antibody does not react with rat albumin or rat IgG either in this ELISA or on Western Blot. Natural cystatin C showed dose-response curves that were parallel to the standard curves obtained using the Ethos Biosciences kit standards, indicating that this kit can be used to determine relative levels of native cystatin C. The assay is conducted in an indirect competitive mode and the results are reported as ng/ml rat cystatin C.