title: Clinical usefulness of serum cystatin C as a marker of renal function.
abstract: BACKGROUND
  Accurate renal function measurements are important in the diagnosis and treatment of kidney diseases. In contrast to creatinine, the production of serum cystatin C has been extensively reported to be unaffected by body muscle mass, age, gender, and nutritional status.
  
  
  METHODS
  Our study included 37 samples from diabetic chronic kidney disease (CKD) patients for whom serum creatinine tests had been requested and 40 samples from a healthy populations in Dong-A University Hospital between May 2010 and June 2010. The assay precision (i.e., the coefficient of variation) and the reference range of the serum cystatin C test were evaluated. We compared the estimated glomerular filtration rates (GFRs) based on cystatin C with those based on creatinine. Moreover, we investigated the influences of age, gender, weight, and muscle mass on serum creatinine and serum cystatin C.
  
  
  RESULTS
  There was a positive correlation between GFR based on creatinine and that based on cystatin C (r=0.79, P<0.0001) among the diabetic CKD patients. Serum creatinine and cystatin C were significantly correlated with body weight and muscle mass, but the strengths of these correlations were greater for serum creatinine. The precision study revealed excellent results for both the high and low controls. The 95% reference interval of cystatin C in the healthy population was 0.371 to 1.236 mg/L.
  
  
  CONCLUSIONS
  Based on these results, we conclude that, despite the strong correlation between serum creatinine and cystatin C, cystatin C is less affected by weight and muscle mass and might represent a better alternative for the assessment of renal function.
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Kwang-Sook
authors.initials: KS
authors.lastname: Woo
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Jae-Lim
authors.initials: JL
authors.lastname: Choi
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Bo-Ram
authors.initials: BR
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Jin-Yeong
authors.initials: JY
authors.lastname: Han
keywords: Renal function; Serum creatinine; Serum cystatin C