title: Cystatin C versus creatinine in determining risk based on kidney function.
abstract: BACKGROUND
  Adding the measurement of cystatin C to that of serum creatinine to determine the estimated glomerular filtration rate (eGFR) improves accuracy, but the effect on detection, staging, and risk classification of chronic kidney disease across diverse populations has not been determined.
  
  
  METHODS
  We performed a meta-analysis of 11 general-population studies (with 90,750 participants) and 5 studies of cohorts with chronic kidney disease (2960 participants) for whom standardized measurements of serum creatinine and cystatin C were available. We compared the association of the eGFR, as calculated by the measurement of creatinine or cystatin C alone or in combination with creatinine, with the rates of death (13,202 deaths in 15 cohorts), death from cardiovascular causes (3471 in 12 cohorts), and end-stage renal disease (1654 cases in 7 cohorts) and assessed improvement in reclassification with the use of cystatin C.
  
  
  RESULTS
  In the general-population cohorts, the prevalence of an eGFR of less than 60 ml per minute per 1.73 m(2) of body-surface area was higher with the cystatin C-based eGFR than with the creatinine-based eGFR (13.7% vs. 9.7%). Across all eGFR categories, the reclassification of the eGFR to a higher value with the measurement of cystatin C, as compared with creatinine, was associated with a reduced risk of all three study outcomes, and reclassification to a lower eGFR was associated with an increased risk. The net reclassification improvement with the measurement of cystatin C, as compared with creatinine, was 0.23 (95% confidence interval [CI], 0.18 to 0.28) for death and 0.10 (95% CI, 0.00 to 0.21) for end-stage renal disease. Results were generally similar for the five cohorts with chronic kidney disease and when both creatinine and cystatin C were used to calculate the eGFR.
  
  
  CONCLUSIONS
  The use of cystatin C alone or in combination with creatinine strengthens the association between the eGFR and the risks of death and end-stage renal disease across diverse populations. (Funded by the National Kidney Foundation and others.).
authors.affiliation: Division of General Internal Medicine, San Francisco Veterans Affairs Medical Center, and Department of Medicine, University of California San Francisco, San Francisco, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Shlipak
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Matsushita
authors.forename: Johan
authors.initials: J
authors.lastname: Ärnlöv
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Inker
authors.forename: Ronit
authors.initials: R
authors.lastname: Katz
authors.forename: Kevan R
authors.initials: KR
authors.lastname: Polkinghorne
authors.forename: Dietrich
authors.initials: D
authors.lastname: Rothenbacher
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Sarnak
authors.forename: Brad C
authors.initials: BC
authors.lastname: Astor
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Levey
authors.forename: Ron T
authors.initials: RT
authors.lastname: Gansevoort
mesh_terms: D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000209:etiology; D007677:Kidney Function Tests; D012015:Reference Standards; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000401:mortality / Q000503:physiopathology*; D012306:Risk; D018570:Risk Assessment / Q000379:methods
chemical_list: D055316:Cystatin C; D003404:Creatinine