Cystatin C(Cys C) Determination Reagent(Latex Immunoturbidimetry) is an in vitro diagnostic quantitative test kit. CysC is a cysteine protease inhibitor with a molecular weight of 13.3KD, also known as γ-microglobulin or γ-postglobulin. Circulating CysC, cleared only by glomerular filtration, is an endogenous marker that reflects change of glomerular filtration rate, and it is reabsorbed in proximal convoluted tubule, completely metabolized and decomposed and not returned to blood. Therefore, the blood concentration of CysC is determined by glomerular filtration, not other external factors like sex, age and dietary. So CysC is an ideal endogenous marker that reflects change of glomerular filtration rate.