What is Cystatin C?
Cystatin C is an alternative endogenous filtration marker to creatinine. It is a 13-kDa protein produced by all nucleated cells.
It is freely filtered by the glomerulus and then catabolized by the proximal tubule cells but does undergo extrarenal elimination. Because cystatin C is filtered and destroyed, only small amounts of cystatin C are excreted in the urine and its urinary clearance cannot be measured.
Although the generation of cystatin C is less variable and less affected by age and gender than serum creatinine, it is now recognized that there are non-GFR determinants of cystatin C.
Several studies have shown that eGFRcys is more strongly associated with long term adverse events such as death and cardiovascular disease.
It is possible that this stronger association is due to the presence of these nonGFR determinants.
