title: Cystatin C as a marker of glomerular filtration rate:  prospects and limitations.
abstract: OBJECTIVE
  There is much interest in cystatin C to replace or supplement serum creatinine to estimate the glomerular filtration rate (GFR). Here we review the performance of cystatin C and combined creatinine-cystatin C estimating equations compared to creatinine-based estimating equations in chronic and acute kidney disease.
  
  
  RESULTS
  Drift in the cystatin C assay has had a large effect on the results reported using cystatin C, but these issues are not routinely considered in evaluation of GFR-estimating equations. The recently released primary reference material for cystatin C will allow less difference among assays in the future. There does not appear to be a consistent message among published studies as to whether cystatin C-based equations are better than creatinine-based equations in the general population or those with chronic kidney disease (CKD), as well as those with reduced muscle mass or chronic illness, or acute kidney injury. Cystatin C could be used in combination with creatinine as a confirmatory test for estimated GFR from creatinine.
  
  
  CONCLUSIONS
  Cystatin C may have a role to estimate GFR in selected circumstances, and the next set of studies should be directed at developing implementation strategies for its use.
authors.affiliation: Tufts Medical Center, Boston, Massachusetts 02111, USA. LInker@tuftsmedicalcenter.org
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Inker
authors.forename: Aghogho
authors.initials: A
authors.lastname: Okparavero
mesh_terms: D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood* / Q000502:physiology / Q000592:standards; D003920:Diabetes Mellitus / Q000097:blood; D005919:Glomerular Filtration Rate; D006801:Humans; D009135:Muscular Diseases / Q000097:blood; D051437:Renal Insufficiency / Q000097:blood / Q000503:physiopathology / Q000628:therapy; D017582:Renal Replacement Therapy; D019737:Transplants
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine