摘要Objective:To investigate the clinical usefulness in terms of estimation for glomerular fil tration rate(GFR), we determined the serum cystatin C levels in 72 healthy adult s , 63 children, and 109 patients with various renal diseases, and compared the s erum cystatin C concentrations with serum creatinine levels. In addition, the re nal function was evaluated in 5 adults receiving renal transplantations using cy statin C.Methods:Serum cystatin C levels were measured by a par ticle-enhanced nephelometric immunoassay on Dade Behring nephelometer system. Se rum and urine creatinine concentrations were determined by use of Jaff's kinetic assay.Results: The cystatin C concentration at birth was typica lly double that found in adults, then fell to a constant level after 1 year, a v a lue that was maintained to about 60 years. The studies of cystatin C in the elde rly showed that the circulation cystatin C levels rose gradually above 60 years. There was a significant positive correlation between serum cystatin C and creat inine level (r=0.921,P＜0.01) in the patients with various renal diseases. S erum cystatin C was inversely and logarithmically correlated with creatinine cle arance as shown in the equation lg cystatin C =-0.6061gCCr+1.209(r=-0.887,P ＜0.01). Serum cystatin C levels rose prior to creatinine concentrations and sta rted to increase over normal range when creatinine clearance remained within no rmal range. After renal transplantation,cystatin C concentration significantly d e creased during the first week(-43% vs -21% for creatinine) in patients without d elayed graft function. In some cases of acute renal impairment, the increase in serum cystatin C values was more prominent than that of creatinine.Conclusion:Serum cystatin C is probably more attractive for esti mation of renal function than serum creatinine and creatinine clearance especial ly for detection of the mild reduction of glomerular filtrate rate in patients w ith various kidney diseases. Serum cystatin C can also be used as an alternative marker of allograft function in adult transplant patients.