Serum cystatin C as an endogenous marker of the renal function - a review

Since 1985, cystatin C has been suggested to be a marker of the renal funct ion. Cystatin C is a proteinase inhibitor with a low molecular weight (M-r = 13359). It is produced at a constant rate in all nucleated cells investig ated to date, freely filtered in the renal glomeruli and reabsorbed and cat abolised in the proximal tubules. The concentration of serum cystatin C is mainly determined by glomerular filtration, which makes cystatin C an endog enous marker of glomerular filtration rate (GFR). There are few data descri bing the influence of various factors on the production and elimination of cystatin C. Fully automated assays using particle-enhanced turbidimetry or particle-enhanced nephelometry are available and the assays are precise, ra pid and usable in clinical routine practice. Reference intervals have been determined for cystatin C in adults and in children older than one year. It has been suggested that the same reference interval can be used in childre n older than one year and in adults without gender differences, on the assu mption that the same method with the same standardisation is used. Several studies including adults and children with different renal diseases with va rious kidney function have suggested serum cystatin C to be a better marker of GFR than serum creatinine.