title: Cystatin-C and inflammatory markers in the ambulatory elderly.
abstract: OBJECTIVE
  Inflammatory factors are elevated in persons with severe renal dysfunction, but their association across all levels of renal function is unclear. We compared cystatin-C, a novel marker of renal function, with creatinine and estimated glomerular filtration rate (eGFR) as predictors of C-reactive protein and fibrinogen levels.
  
  
  METHODS
  This study is a cross-sectional analysis to evaluate cystatin-C, creatinine, and eGFR as predictors of the inflammatory markers C-reactive protein and fibrinogen. Participants included 4637 ambulatory elderly patients from the Cardiovascular Health Study. Multivariate linear regression was used to determine the independent associations of each renal function measurement with the inflammatory marker outcomes.
  
  
  RESULTS
  After adjustment for confounding factors, cystatin-C was correlated with both C-reactive protein (coefficient = 0.13; 95% confidence interval: 0.10-1.16, P <.0001) and fibrinogen levels (0.15; 0.13-0.18, P <.0001). Associations were larger than those for creatinine and C-reactive protein (0.05; 0.02-0.07, P = .003) or fibrinogen (0.07; 0.04-0.10, P <.0001). Adjusted levels of C-reactive protein increased incrementally across quintiles of cystatin-C, from a median of 2.2 mg/L in quintile 1 to 3.7 mg/L in quintile 5. In contrast, both C-reactive protein and fibrinogen had U-shaped associations with quintiles of creatinine and eGFR, because the inflammatory markers were equivalently elevated in quintiles 1 and 5.
  
  
  CONCLUSIONS
  The finding of a significant linear association of cystatin-C and inflammation markers suggests that even small reductions in renal function may be associated with adverse pathophysiologic consequences.
authors.affiliation: General Internal Medicine Section, San Francisco Veterans Affairs Medical Center and Department of Medicine, University of California, San Francisco, Calif 94121, USA. shlip@itsa.ucsf.edu
authors.forename: Michael G
authors.initials: MG
authors.lastname: Shlipak
authors.forename: Ronit
authors.initials: R
authors.lastname: Katz
authors.forename: Mary
authors.initials: M
authors.lastname: Cushman
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Sarnak
authors.forename: Catherine
authors.initials: C
authors.lastname: Stehman-Breen
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Psaty
authors.forename: David
authors.initials: D
authors.lastname: Siscovick
authors.forename: Russell P
authors.initials: RP
authors.lastname: Tracy
authors.forename: Anne
authors.initials: A
authors.lastname: Newman
authors.forename: Linda
authors.initials: L
authors.lastname: Fried
mesh_terms: D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000032:analysis*; D002097:C-Reactive Protein / Q000032:analysis; D003430:Cross-Sectional Studies; D055316:Cystatin C; D015891:Cystatins / Q000032:analysis*; D005260:Female; D005340:Fibrinogen / Q000032:analysis; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000175:diagnosis*; D008297:Male; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D005340:Fibrinogen; D002097:C-Reactive Protein