Cystatin C Immunoparticles is polyclonal rabbit antibody to cystatin C covalently coupled to polystyrene particles. In conjunction with Dako Cystatin C Calibrator (X0974), the Cystatin C Control Set (X0973), and Dako Turbidimetry/Nephelometry Reaction Buffer 9 (S2361), the Cystatin C Immunoparticles form a 'kit' intended for the quantitative determination of cystatin C in human serum and plasma by turbidimetry and nephelometry.

Cystatin C is a small, 13 kDa, non-glycosylated basic protein belonging to the cystatin super-family of cysteine protease inhibitors. Cystatin C is produced by virtually all nucleated cells, and is present in all body fluids investigated. The production rate is constant and is unaffected by inflammatory processes, gender, age and muscle mass (1). In the normal kidney, cystatin C is almost freely filtered through the glomerular membrane and then nearly completely reabsorbed and degraded by the proximal tubular cells. Therefore, the plasma concentration of cystatin C is almost exclusively determined by the glomerular filtration rate (GFR), making cystatin C an excellent indicator of GFR. Numerous studies and a meta-analysis incorporating 4492 subject samples have shown that serum cystatin C is clearly superior to serum creatinine as a marker for GFR (2). Measurement of the serum/plasma cystatin C concentration allows for estimation of GFR using one simple equation for patients from four months old to 93 years old.

Application Notes for the cystatin C determination on Cobas and Hitachi automated instruments are available on request and Application Notes for a number of other instruments have also been prepared.